For the organisation: free
Registering the school, PTA or club and using its dashboard costs nothing.
For the school's families: free within the Space
Signing up and talking to other families in the same Space is free. Credits are only used to message families outside the school (for example in Travelling Families or My City), and each family gets 3 free credits when they complete their profile.
School trips with no commitment
Asking for information about a school trip from the dashboard doesn't commit you to anything, and Woltica doesn't charge for it.