Places and the waiting list belong in the same system. When a space frees up, the next family in the queue has to be contacted automatically — otherwise it sits empty for a fortnight while thirty people wait.
Attendance here is a safety matter. Who is in the water needs to be established before the lesson starts, and the number of children per teacher isn't a guideline but the basis of supervision.
Re-enrolment for the following term is the calmest income there is and the easiest to lose. Asking current families before general sign-up opens fills half the places before the rush even starts.