I do believe hundreds of millions of people have searched for "free VPN" in play store, looked at the great ratings, installed one of them and it even worked perfectly so they rate they all 5 stars too and tell everyone at school.

The numbers are so high because the grift works well. Offer a free VPN service, turn it into nodes for your residential proxy network and rent it out for spam, crawling, ddos or whatever.

Forget about schools, manage any large enough corporate environment and you've heard of most of these. The moment management software blocks the install of a product you can expect you expect an angry demand for an explanation, and ive been on the receiving end of such demands for basically every free VPN product ever.