Building an exercise bank that lasts

Why folders are not enough

The most common setup looks like this: one folder per course, subfolders per session, and inside them files named exercise2, exercise2_solution, exercise2_v3_final. It works — as long as you remember the context.

The problem shows up two years later. You are looking for “that loops exercise that went down well with the career-change group”. It exists, you are sure of it. But was it in the March folder or the September one? And in which version?

Three structural weaknesses explain the failure:

• Classification is a tree: an exercise can only live in one place, while it often belongs to two themes at once.
• The solution is a separate file, eventually mislaid or handed out at the wrong moment.
• Nothing records what worked: the file keeps no trace of the group, the actual running time, or the fact that it ran long.

The base unit: one exercise, one brief, one solution

A bank holds up if the filing unit is the right size. Not the whole course — too large, never reusable as is — nor the isolated question — too small, without context.

The right grain is the exercise: a brief that fits on one screen, a solution alongside it, and enough to place it. Each entry benefits from four pieces of information, no more:

• A title, phrased as what the learner must do, not as a number.
• The subject or theme, so search can find it.
• The level, even if only beginner / intermediate / advanced.
• The actual duration observed in class — not the one you estimated while writing it.

That last one is the most valuable and the most often skipped. Knowing an exercise's real duration transforms preparation: you compose a day by assembling blocks whose weight you know.

Start with what already exists

The temptation, when building a bank, is to import everything from scratch. That is the surest way never to begin.

The method that works is the opposite: feed the bank as your sessions go. At the next course, instead of reopening last year's file, enter the exercise into the bank. You are not working more — you are working in the same place as before, but tidied.

After three or four sessions, the bank covers most of what you actually use. The exercises you have not pulled out in two years will be missed by nobody: that is natural selection by the field, and it beats exhaustive archiving.

A useful marker: a living bank rarely holds more than fifty exercises per course. Beyond that, you have usually archived instead of sorting.

The solution, and when it appears

Solutions raise a practical problem that folders handle badly. If the solution sits in a file next door, you must remember not to hand it out too early — and a single group email is enough to make the exercise pointless.

Attaching the solution to the exercise itself, but under your control, settles the matter: the brief goes to the class, the solution stays on your side, and you decide when it becomes visible. Same logic as correcting at the board, except it no longer depends on your vigilance over attachments.

That detail also changes how you write the solution. Since it will be read on screen afterwards, it gains from explaining the reasoning rather than only giving the answer.

Finding, reusing, adapting

A bank serves three different purposes, and it is worth telling them apart.

Finding is the daily use: a search on a word from the title or theme should be enough. If you have to remember where the exercise is filed, the classification has already failed.

Reusing as is applies to proven exercises, the ones that work every time. They form your base layer: project them, send them, leave them alone.

Adapting is the most frequent case in practice. The same exercise serves as a starting point, with a different dataset or one extra constraint depending on the audience. Duplicate then modify beats rewriting: the original stays available for the next group.

What the bank gives back to preparation

The benefit does not show in the first week. It appears at the third session, when preparing a day stops being writing and becomes assembling.

You know what you have, how long each block takes, and what worked with which kind of group. Preparation shrinks to choosing an order and adjusting a duration or two. The time saved does not vanish: it moves to what matters, namely running the session and the learners who are struggling.

It is also what makes a course transmissible. A colleague taking over your module inherits situated, timed exercises, not a pile of files to decode.