If the limitations on conducting A/B tests on people under 13 are enforced, you will need a driver's license to connect to the internet, and you will need to show it to every website.
Surely a state ID is enough, right? I know at least 3 legal adults in my circles alone without a driver's license, though I believe they all have either a state ID or permit. (Not that I support requiring any sort of meatspace identification for acting in cyberspace).