Could be what's called "exertion headaches". I used to get these a couple years ago when I took 6 months off from lifting weights and then got back in the gym, I'd get exertion headaches towards the end of and after every workout. I talked to a doctor about them and he said to rest and get lots of sleep and take a few days off and then taper up from light workouts slowly back up to the hard workouts.
Hope that helps. If they are exertion headaches and not from being strangled in class then it's probably good news because they aren't dangerous and are easy to beat. It only took me a couple weeks of resting and slowly easing back into lifting to overcome them.