People join in the middle. Somebody who needs a certificate by June enrols in February, and slotting them into a group that started in October is the recurring problem this kind of school actually has.
A placement result is useless until it becomes a seat. The level, the availability and the timetable have to meet in one place, otherwise a student who tested on Monday is still waiting on Friday and has started looking elsewhere.
Viability moves constantly. Every arrival and departure changes whether a group still works, and merging two half-empty levels is a decision that has to be taken while both still have students in them.
Companies buy differently from individuals. Invoices to a finance department, attendance reports for whoever authorised the training and classes delivered on the client's premises: none of that fits the process built for a person paying monthly.