I have undertaken all kinds of bits of training in the USA and for several of them I required TSA approval prior to the course, but in no case did I do anything special about visas. The M1 visa allows full-time residence at a college, an extended stay, and certain working privileges - it is aimed at real full-time university students.
On the other hand, the normal B1/B2 visa waiver allows only 90 days in the country, and has no work privileges, but allows you to do any number of recreational activities you like - including taking checkrides, if that is what turns you on.