I'm pretty certain that Freedom (and many other ad-blocking apps) got banned because they were using a VPN for uses other than a strict VPN. Your app uses a VPN for access control, right? Why do you think it won't be banned?
EDIT: I don't want that to sound hostile at all...genuinely curious
Fair question. There are a number of differences between apps like Freedom and StudyCity. We are aware of the recent VPN rules. StudyCity simply needs a gate to direct the student / child to take a couple of minutes to earn points on Khan Academy or another supported site. The gate can be implemented in many ways. At the moment, this is all the detail I can provide.