CultofMac has a great review of the headphones I started using in my lab last year. Sonically I prefer the semi-open AKG-style, but for holding up in class these are the absolute best you can buy.
At the beginning of the year, we went through three different models in actual classroom use: The Sennheiser HD201, the AKG K240, and the Shure SRH440. The Sennheisers are super cheap, which is good if you’re on a tight budget I suppose, but they will only last about a year or two before the hinges snap.
The AKG’s *should* have worked well. They’re very flexible, but not in a hinge-snappy kind of way. The problem I had with these is that after a short use period, the electrical contacts in the ear cups would start to fail. Back when they made these in Austria I never encountered this problem, but the newest batches are Chinese-made and must not have a reliable production method yet.
The Shure SRH440, on the other hand, is built like a truck. These are the most solid headphones I’ve ever used – all metal, and still pretty comfortable. The backs are closed, which make them a bit worse for mixing than the AKG’s, but for general class use they can’t be beat.