Hey MedHacker-
That route will be absolutely nuts every morning. Both 676 and 76 are horrific to commute on, however, there really isn't a great way to do it without using one of them. 21 minutes is a laugh of an estimate--I'd say it's closer to 35 on a good day and a very serious "who-knows" on a bad day. You could take 676 to the art museum, and then use either West River Drive or Kelly Drive to get to City Ave--the flow of traffic on these streets is mostly into the city, where you'll be going away from the city. Hopes this helps, but if classes are at 8AM, I'd be prepared to leave at 7... If anyone else has any questions about commuting and/or Philadelphia in general, let me know--I've lived in or around Center City for almost 8 years now.