Undo the last click
Every mark puts a strip above the grid naming what it replaced — "Alvarez, Kyle Matthew on 3 September: present → absent" — with Undo that beside it. Undo puts back exactly what was there, including clearing a first-ever mark back to blank.
Recent changes
Under the register, Recent changes lists the last eight marks on this class: the learner, the day, what the mark replaced, when it happened and who made it. If a day looks wrong and you have already moved on, check here first.
A week you have finished locks itself
Only the current week is open. An earlier week is read-only, and a click on it answers: "That week is already recorded. Open it for editing first — the lock is there so a stray click cannot change a day you finished."
- In the header above the grid, click the locked week's dates. It carries a padlock.
- Correct the day.
- Click the same dates again to close the week.
Clearing a whole month
Mark everyone present clears every mark in the month shown, after a confirmation that names the month. Everyone counts as present for that month again.
Two things are spared: weeks you have not opened, and a term whose cards are released. The toast tells you when marks were held back — "N in closed weeks stayed as recorded."
Nothing is quietly lost
Every mark, every clear and every undo is written to the class's audit trail with what it replaced. That is what Recent changes reads, so a correction is always traceable rather than something you have to remember.