It very much is. Free VPNs almost always have some sort of catch. E.g. HolaVPN users agree in the ToS to become an exit node for other VPN users: https://en.wikipedia.org/wiki/Hola_(VPN)

If social media is so compelling, then teens almost certainly will take whatever steps are necessary to access it.

Proton has a good free offering.

That's not the point though. The kids can just not get a VPN, and instead do something else with their time.