The KS3 map behind Heddy: 700 concepts, and what has to come first
Heddy does not teach from a blank chat window. It teaches from a map: 700 named KS3 concepts and 1,147 prerequisite links across seven subjects, where every link says what must come first, and why. It is the same map the professors teach from — and in the app you can tap any bright dot and trace the chain backwards yourself.
A student stuck on equations is rarely stuck on equations
Here is the most common thing that happens in tutoring, and the thing a chat window is worst at.
A student says: I don't get solving equations. They have done the lesson. They have watched the explanation. They can even repeat the rule back. And they still get it wrong, in a way that looks random from the outside — right on Tuesday, wrong on Thursday, wrong again on the practice paper.
Almost always, they are not stuck on solving equations. They are stuck two or three steps back, on something nobody thought to re-check because it belongs to a topic that was signed off last year. Maybe it is what a negative number does when it crosses the equals sign. Maybe it is that both sides have to stay equal — the idea the whole method rests on, which was taught once, in Year 7, using a picture of a balance, and quietly never revisited.
An answering machine cannot find that. Ask it about solving equations and it will give you a very good explanation of solving equations. It will be correct, it will be clear, and it will land on exactly the same spot that failed the first time. The student nods, the confusion survives intact, and everyone concludes they are "just not a maths person".
What lets a tutor do better is not being cleverer at explaining. It is knowing what sits underneath the thing being asked about — and being willing to go there instead.
What the map actually is
The map is that underneath, written down.
700 named concepts. 1,147 prerequisite links. Seven subjects — maths, physics, chemistry, biology, English, geography and history. Everything between eleven and fourteen, in the order it depends on.
Two words there are doing the work.
Named. Not "algebra" as a vague region, but individual ideas with individual names, each of which a student can be fluent in, shaky on, or missing entirely. A topic is too coarse a unit to diagnose with. You cannot be "45% at algebra" in any way that tells you what to do on Thursday night. You can, however, be solid on one named idea and missing the one it rests on, and that is an actionable sentence.
Prerequisite. The links are directional. They do not say "these two things are related" — a search engine can tell you that. They say this must come first, and why. That "why" is the part that makes the map teachable rather than merely a diagram: when a professor walks a student back down a link, it can say what the earlier idea contributes to the later one, which is exactly the sentence that makes the fog lift.
And it is not a separate artefact that marketing drew. It is the same map the professors teach from — Pi in maths, Newton in physics, Curie in chemistry, Darwin in biology, Quill in English, Harari in history, Mercator in geography. Each one owns a subject, and each one is reading the same graph you can tap through in the app.
The kind of chain the map holds
Take balancing a chemical equation — the thing that makes a whole Year 8 class go quiet.
A student cannot balance an equation until they can write the formulae correctly, because you cannot conserve atoms you have written down wrong. They cannot write the formulae until they know how elements combine — which ones want to give electrons away, which ones want to take them, and in what ratio that leaves. And that, in turn, rests on the structure of the atom itself: what is in the shells, and why the outer one decides the chemistry.
Four ideas, three arrows, one direction of travel. A student failing at the top of that chain might have a problem anywhere along it — and the four possible fixes are completely different lessons. Re-teaching balancing to somebody who cannot write a formula is not slow progress. It is no progress, performed thoroughly.
Maths has the same shape. Solving a two-step equation depends on confidently undoing an operation with its inverse, which depends on the idea that whatever you do to one side you do to the other, because the two sides stay equal. Nobody arrives stuck at the bottom of that chain on purpose. They arrive there because the bottom was covered quickly, a long time ago, and has been silently load-bearing ever since.
That is the kind of chain the map holds — hundreds of them, across seven subjects, each link carrying its reason.
What the map does on an ordinary Tuesday
None of this would matter if it only existed as a picture. It does three specific jobs.
It decides what a student is ready to learn next. Readiness is not "what comes next in the textbook" — it is whether the things a concept depends on are actually in place. When they are, a lesson lands in one sitting. When they are not, the same lesson costs three sittings and still does not stick. The map is how that question gets answered before the session rather than discovered halfway through it.
It is the order behind "anything you miss comes back as a card." Everything a student misses in a session comes back as a flashcard — that part is simple. The map is what decides which card, and in what order. A missed step that sits at the bottom of a chain is not the same as a missed step at the top: one of them unblocks four other things, and the other does not. Cards built from your own mistakes are already the ones that move a grade; ordering them by the graph is what stops you drilling the symptom while the cause sits untouched. (The same logic sorts the ready-made decks in the Atlas.)
It is why a mistake gets traced downwards instead of re-explained. This is the one students feel. Get something wrong twice in the same way and the professor does not say the same sentence louder — it goes down a link and checks the idea underneath. Often the correction happens a full level below the question that was asked, and then the original question stops being hard on its own. It pairs with the hint ladder, which refuses to hand over the answer: a tutor that will not simply tell you needs somewhere honest to go instead, and going backwards along a prerequisite link is that somewhere.
It is also what a teacher sees. Where a class keeps slipping, traced back to the idea underneath — not a list of low scores, but the shared link they are all failing to cross.
What it doesn't do, said plainly
The map is a curriculum, not a verdict. It does not rank students, it does not produce a grade, and it does not decide that anyone is a certain sort of learner. It holds what depends on what, and leaves the teaching to the professors and the thinking to the student.
It is also, today, KS3 only — ages eleven to fourteen, seven subjects. GCSE is planned next, and until it exists we would rather say so than imply coverage we do not have.
And it is visible on purpose. Open the KS3 map in the app, tap any bright dot, and the chain behind it lights up. That is not a decoration. A student who can see that the thing they are stuck on has four things underneath it has already learned the most useful fact about being stuck: it is usually somewhere else, and it can be found.
Heddy is free to download on the App Store, and the flashcards are free forever — no card details, no sign-up to look around. Tutoring turns are what a plan pays for, and a grown-up buys plans on aitutors.me, never in the app.
Updated 23 Sep 2026. Written by Duke Harewood, who builds the tutors at aitutors.me.