A letter to my students

Thank you for the past five years.

I wish you all the best in what comes next.

I have loved teaching you,
and I hope I've inspired you
as much as you've inspired me.

"Lions do not concern themselves
with the opinions of sheep."

— Tywin Lannister · Game of Thrones
— Mr. D
dexstem
For the year ahead

Where are you headed?

Four pathways for the summer. Pick yours, work through the checklist, and copy the AI tutor prompt — paste it into ChatGPT, Claude, or Gemini and you'll have a tutor that already knows where you're going and what you need to learn.

US → UK

US Grade 5 / 6 → UK Year 6 / 7

Moving from the American system into a British school. The big shifts: SATs-style grammar terms, ratios and percentages earlier, and split sciences.

Open pathway
Y8 → Y9 · Pre-IGCSE

Grade 7 / Year 8 → Year 9

The final year before IGCSEs begin. This summer is the moment to get fluent in algebra, lock in scientific method, and start writing analytical essays.

Open pathway
Y9 → Y10 · IGCSE Year 1

Grade 8 / Year 9 → Year 10

IGCSE begins. Two years of work that ends in real external exams. Hit the ground running with the foundations every Year 10 teacher expects.

Open pathway
MYP · IB Middle Years

Joining or leaving MYP

The IB Middle Years Programme is concept-driven, inquiry-based and uses ATL skills. Whether you're moving in or moving out, here's how to bridge the gap.

Open pathway
Pathway 01

US Grade 5/6 → UK Year 6/7

The UK curriculum moves faster on some things and slower on others. By Year 6 you're expected to know grammar terms American schools don't teach (fronted adverbials, modal verbs, subordinate clauses), do long division and percentages confidently, and sit national tests (SATs). In Year 7 you start secondary school — sciences split into Biology, Chemistry, and Physics, and you'll use letters in algebra from week one.

Maths

English

Science

Video + practice

Best for clear video explanations. Free, no account needed to watch.

Textbooks + Flexi AI

Full free textbooks with practice. Flexi is their built-in AI tutor.

UK-specific revision

Built for the British curriculum. Short, flash-card style.

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Copy this into ChatGPT, Claude, or Gemini

Paste it as your first message. The AI will know what you're studying and how to teach you.

I'm a student moving from the American curriculum (Grade 5/6) into the British curriculum (Year 6/7). I have around 6 weeks of summer to bridge the gap before school starts.

The British system is ahead on a few things and uses different terminology, so I need help with:

MATHS — long division, fractions arithmetic, percentages of amounts, ratio and proportion, BIDMAS, negative numbers, area/perimeter of basic shapes, intro to algebra using letters.

ENGLISH — UK grammar terms (fronted adverbials, modal verbs, subordinate clauses, determiners), formal punctuation (semicolons, colons), and how to write in a formal register.

SCIENCE — basics of biology (classification, evolution), chemistry (states of matter, mixtures), and physics (circuits, forces). I want to be confident with "fair test" structure: variables, prediction, method, results.

Please be my tutor. Each session:
1. Ask which topic I want to work on.
2. Explain it at Year 6/7 level with one short example.
3. Give me 3 practice questions, one at a time, and check my work.
4. Tell me what to review tomorrow.

Start by asking me which subject I want to begin with and how confident I feel (1–5) in each area listed above.
Pathway 02

Grade 7 / Year 8 → Year 9

Year 9 is the runway. IGCSEs start the year after, so this summer is where you turn shaky algebra into automatic algebra, learn to write a real analytical paragraph, and stop being scared of equations in science. Get this summer right and Year 10 feels easy. Get it wrong and you spend Year 10 catching up.

Maths

English

Sciences

Video + practice

Strongest for maths and science explanations. Free.

Textbooks + Flexi AI

Algebra and life science FlexBooks are the gold standard.

UK-specific revision

KS3 covers everything Year 9 expects. Practice in 5-min bursts.

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Copy this into ChatGPT, Claude, or Gemini

The AI will know what level you're working at and what's coming next year.

I'm going into Year 9 of the British curriculum this September. Next year I start IGCSEs, so this summer I need to get really solid on the foundations.

MATHS — I need to be fluent in: simplifying/expanding/factorising algebra, solving linear and simultaneous equations, straight-line graphs (y = mx + c), Pythagoras' theorem, right-angle trigonometry (sin/cos/tan), index laws, standard form, basic probability, and finding mean/median/mode/range.

ENGLISH — I need to write good PEEL paragraphs (Point, Evidence, Explain, Link), analyse the *effect* of language techniques (not just name them), and feel comfortable with at least one Shakespeare play.

SCIENCE — Biology: cell structure, respiration & photosynthesis equations. Chemistry: atoms, the periodic table, balancing equations. Physics: speed-distance-time, Newton's three laws, energy stores and transfers.

Please be my tutor. Each session:
1. Ask me which subject and topic.
2. Diagnose with one quick question to see where I'm at.
3. Teach the bit I'm weakest on, with one worked example.
4. Give me 3 practice questions and mark them.
5. Tell me one thing to review before next session.

Start by asking which subject I want to begin with and how confident I am (1–5) in each topic above. Be encouraging but honest — I'd rather you tell me I'm wrong than let me drift into Year 10 thinking I'm fine.
Pathway 03

Grade 8 / Year 9 → Year 10 · IGCSE Year 1

IGCSE begins in September. Two years of work, then real external exams that universities and Sixth Forms will see. The single biggest predictor of a good IGCSE grade is how solid your Year 9 foundations are when you walk in. This summer, lock them in.

Staying at Wycombe?

You're on Edexcel — start with past papers.

Wycombe runs Pearson Edexcel International GCSE. The single most underrated revision tool is to look at a real past paper before you start studying — you see the style of question, the command words, and the way mark schemes reward (or punish) specific phrasings. Print one, try it cold, then revise the gaps it exposes.

Save My Exams
Cleanest UI. Papers + mark schemes + topic questions, filterable by year and tier. The one most students end up using.
IGCSE Maths Bio Chem Phys Eng Lang Eng Lit
Physics & Maths Tutor
Sciences and maths gold standard. Worked solutions to *every* question on every paper — closest thing to a personal tutor.
PapaCambridge
The deepest archive — old papers going back decades, exam reports, examiner reports. Great for finding patterns and recurring topics.
Maths Genie · IGCSE
Maths only. Video solutions for every past paper question. If you're nervous about maths, start here.
edexcelpastpapers.com
No-frills paper dumps organised by year. Useful when you just want the PDF without browsing.
BBC Bitesize
Not past papers — but the best free explanations of concepts when a paper exposes a gap. Hit Bitesize, then go back to the paper.

💡 The play: grab the most recent Maths A paper, try it cold, mark yourself honestly, then use Save My Exams or PMT for the worked solutions on anything you missed. One paper a week from now till September and you walk into Year 10 already winning.

Maths (IGCSE foundations)

English Language & Literature

Sciences (Bio · Chem · Phys)

Video + practice

Best US-curriculum equivalents to IGCSE topics.

FlexBooks + Flexi AI

Algebra & sciences as full textbooks — work through chapters one at a time.

IGCSE-specific

Look for your exact board (Cambridge / Edexcel) when you sign up.

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Copy this into ChatGPT, Claude, or Gemini

Replace [Cambridge / Edexcel] with your actual exam board when you know it.

I'm starting IGCSE Year 10 in September. My exam board is [Cambridge / Edexcel — replace with yours].

I need to be solid on the Year 9 foundations BEFORE September so I can hit Year 10 running. Help me revise:

MATHS — rearranging formulas, solving quadratics by factorising, solving inequalities, sketching quadratic/cubic/reciprocal curves, SOH CAH TOA both ways, basic circle theorems, vectors in column form, cumulative frequency and box plots, surds, fractional and negative indices.

ENGLISH — write a strong 4-paragraph PEEL essay in 45 minutes, analyse unseen poetry, do descriptive writing that shows rather than tells. I'll tell you which IGCSE set text my school uses.

SCIENCES — Biology: cells, enzymes, circulation, DNA, genetics. Chemistry: ionic/covalent/metallic bonding, moles, rates of reaction, equilibrium. Physics: Newton's laws, momentum, V = IR, waves.

Please be my tutor:
1. Each session, ask which subject and topic.
2. Give me one exam-style question first to diagnose where I am.
3. Teach the gap I show with one worked example.
4. Give me 3 more questions of rising difficulty.
5. End with one piece of advice for the next session.

Start by asking which subject I want first, my confidence (1–5) in each topic above, and whether I'm aiming for Foundation/Core (grades 1–5) or Higher/Extended (grades 4–9). Be honest with me — Year 10 doesn't reward bluffing.
Pathway 04

Joining or leaving the MYP

The IB Middle Years Programme is different. It's concept-driven instead of content-driven — you'll be asked "why" and "so what" before "what". It uses Approaches to Learning (ATL) skills, Global Contexts, and grades on four criteria per subject. Coming from a traditional curriculum or going back to one, the shift can feel disorientating until you know the language.

Concept-friendly content

Strong on the "why" — fits the MYP inquiry style.

Textbook depth

Use FlexBooks to fill subject gaps when you move into a content-heavy curriculum.

For UK-bound MYP leavers

If you're heading into a UK system after MYP, this is the fastest bridge.

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Copy this into ChatGPT, Claude, or Gemini

Two versions — pick the one that matches you and delete the other.

[IF JOINING MYP] I'm joining the IB Middle Years Programme this September. The MYP is concept-driven and uses inquiry, ATL skills, Global Contexts, and four assessment criteria per subject. Help me:

1. Internalise the IB Learner Profile (the 10 attributes) — quiz me until I can list them all from memory.
2. Practice the 5 ATL skill clusters (Thinking, Communication, Social, Self-management, Research) with a real-world example for each.
3. Walk me through the 6 Global Contexts with one statement-of-inquiry example per context.
4. Teach me to interpret command terms (analyse, evaluate, justify, describe) and how they map to MYP assessment criteria A, B, C, D.
5. Help me write reflective learning-journal entries — give me a prompt and feedback on what I write.

Ask me which subject I'll be strongest in so we can ground the examples there.

---

[IF LEAVING MYP, going into a traditional / IGCSE / AP / A-Level system] I'm leaving the IB MYP and entering a more content-driven, exam-based system. MYP rewarded reflection and process; my new curriculum rewards retrieval and timed answers. Help me:

1. Drill subject vocabulary — give me flashcards and quiz me until I'm fluent.
2. Practice timed essay questions (45 min, no prep) and grade me on a real mark scheme.
3. Build a 6-week study plan that switches my study habits from "process" to "retrieval".
4. Run past paper questions on demand and give me model answers afterwards.
5. Spot where my MYP training is hurting me — e.g. too much reflection where the mark scheme wants definitions.

Start by asking which subjects I'm taking, what curriculum I'm moving into (IGCSE, A-Level, AP, national exam), and whether I have any past papers I can share.
One more thing

Whatever curriculum you walk into, whatever room you sit in next year — remember this. The work you put in this summer is invisible to everyone but you. That's the point. The student who shows up in September already fluent isn't lucky. They were quietly relentless when no one was watching.

Be that student.

If you ever miss me

Talk to AI Mr. Dex.

I built an AI version of myself on Flint K-12 — trained on how I teach, the way I explain things, and a lot of how I'd answer if you put your hand up in class. He's not perfect. But he's me-shaped. And he doesn't sleep.

d

An adaptive tutor that knows my voice.

Stuck on a question? Need a concept explained one more time? Lost your notes the night before a test? Open AI Mr. Dex. He'll work through it with you the same way I would — patient, a little sarcastic, and never, ever just hand you the answer.

Talk to AI Mr. Dex
⚠️ Not actually me. I haven't gained consciousness in a server yet. He's an AI trained to teach the way I do — close, but he sometimes hallucinates. If anything sounds wrong, check it. And email the real me if it really matters: dex.d@dexstem.com.
You · 22:47
i don't understand simultaneous equations help
AI Mr. Dex · 22:47
Right — deep breath. Two equations, two unknowns. We're going to *get rid* of one variable so the other becomes obvious. Write them down for me and I'll walk you through it. Or, do you remember what "elimination" means? Tell me what comes to mind first.
You · 22:48
like… adding them together to cancel something?
AI Mr. Dex · 22:48
Exactly that. Good instinct. Show me both equations and we'll find which variable we can cancel first. (See? You already half-knew.)
For the parents

Thank you for trusting me with them.

Five years of pick-ups, conversos, showtimes, and late-night emails about half-finished projects. None of what your children achieved was possible without you behind them.

If you'd like to grab a coffee, talk shop, or sound out an idea — I'd love that. I'm officially unemployed for the next year and will mostly be on a beach drinking coconuts. But the phone's on.

🥥 Available for coffee, consulting, and conversation

Say hi.

Coffee, a quick call, a wild business idea — all welcome.

A quick introduction

Hi, I'm Dex.

I'm a serial entrepreneur and a polymath of the self-taught kind. I've been in Thailand for years and am currently working through the Thai citizenship process — anyone who's tried it will tell you it's a journey.

By training I'm a STEM teacher: physics, chemistry, biology, maths. By temperament I pick up a new discipline roughly every 18 months. So far that's included laser cutting · 3D printing · web design & development · product design · smart-home automation · investment & real-estate · AI tooling for hospitality and education.

These days I split my time between a 1950s heritage shophouse in Yaowarat that we restored room by room, a poker-timer SaaS that quietly runs home games around the world, a smart-lock platform for short-term rentals, and a science-simulation platform for the next generation of curious kids. None of it would be possible without a very patient partner and an outrageous amount of black coffee.

The through-line: I like problems that sit halfway between fix something practical and build something beautiful. Five years of teaching taught me that the best ideas come from people paying very close attention. I'm taking that into whatever's next.

🇹🇭 Bangkok-based 🥥 Currently semi-retired (until I'm not) 📩 dex.d@dexstem.com
A peek inside

The workshop

A few things currently on the bench. Hover for the name, tap to jump to the details below.

Click anything
DH Dexas Holdem /* poker timer SaaS */ Baan Saeng Jan /* 1950s shophouse */ Moonlight Guide /* interactive story */ SparkBench /* science sims */ LockGO /* smart locks */ π Tutoring /* STEM, Y6–A-Level */ /* available */ DEXSTEM · 2026 REV. 01
What I'm building

A few things I've been working on

If any of these are interesting — as a customer, an investor, a collaborator, or just out of curiosity — the door is open.

Live · EdTech

SparkBench

A bench full of tiny experiments, big questions.

A free platform of interactive science simulations. Drop a student in, watch them play, watch them learn. Built for classrooms, students at home, and any teacher who's tired of saying "just imagine the apparatus".

Visit sparkbench.app
Live · SaaS

Dexas Holdem

A poker tournament timer built for real humans.

A modern timer for home games, charity events, and clubs. Voice announcements, multi-device sync, league standings, and a presentation mode that looks beautiful on the big screen. Free tier + Pro.

Visit dexasholdem.com
Live · Hospitality

Baan Saeng Jan · บ้านแสงจันทร์

A heritage shophouse in the heart of Yaowarat.

House of Moonlight — a six-room boutique stay in Bangkok's Chinatown. Original 1950s shophouse, lovingly restored, with a curated guest guide that turns first-timers into locals. Multi-channel: Airbnb, Vrbo, direct booking.

Visit baansaengjan.com
Live · Experience design

The Moonlight Guide

What if a guest guide actually felt like a story?

Twelve interactive features baked into a single page — time-aware atmosphere, a calligraphy companion, lantern lottery, Yaowarat Bingo, mood-based itinerary recommender, and an AI keyword chat. The kind of thing every boutique stay should have.

See the guide
Live · IoT

LockGO

Smart locks, less drama.

A keyless-access platform for short-term rentals, co-living, and offices. Issue time-bound codes, audit who came and went, kill keys you'll never see again. The lock you wish your last Airbnb had.

Visit lockgo.cloud
Available · Now

Private tutoring · STEM

For your child, your nephew, the kid down the road.

Maths and sciences from Year 6 through IGCSE, MYP, and A-Level. Online or in person (Bangkok-adjacent — depending on coconut supply). Limited slots, structured curriculum, weekly progress notes for parents.

Get in touch