Is there a trial before subscribing?

Yes: 14 days free, no credit card. Signup is self-service from the signup page on klasku.id, and the moment it finishes your school has its own address along with a live tenant panel, Parents Portal, and Teachers Portal.

What you put into the school during the trial is your own data — classes, students, schedules, invoices. When you pick a plan, that same school carries on: nothing is rebuilt, nothing is imported twice.