Sorry, but this is wrong. You don't need level 7 skills to ace the university classes. One of my sims, Justin Dyer, just finished a term at University and he got an A+ in all 4 of his courses without even reaching skill level 6.
Justin took two courses in Photography, one course in Violin, and one course in Acting. He finished with Photography skill at level 5 (max), Violin skill at 4.32, and Acting skill at 5.84. The key to his success was probably joining the Art Society, getting to level 2 in the organization, and attending all of its events for extra credit towards his Fine Art major. Of course, Justin also did all of his homework before classes, attended classes on time, and Took Notes. He used his phone to email his professors once a day, after finishing his classes for the day. He prepared an Outstanding term paper and an Excellent presentation but didn't turn them in until his professors reported that he was a stellar student. That's been my approach every time I've sent a Sim to university and so far it has always worked.