VWP to F-1 Visa

Hello!

A friend of mine got accepted in a university in the US, so he's gonna get a F-1 Visa, being allowed to enter the US as soon as 30 days before the start of his classes. However, he doesnt have the Visa yet and he plans to travel to the US on VWP (prior to those 30 days) and then change the status while he's there. Is that doable/legal?