Re: Age check = ID
This is about mature content, so they should check maturity instead of age. Something like: "write a minimum of 40 explicit and/or double-entendre words in the access field". Or: "select all pictures of adult actors and actresses". Or: "do you see dolphins or kissing humans?". Or: "write down the full time-dependent Hamiltonian for a two-spin system".
Come to think about it, you could start a broad public education campaign based on such an access system.