Kai-- perhaps it used to be that way-- but the treatment of functions from a conceptual stance (rather than a procedural one), the inclusion of trigonometry, and advanced concepts which used to be in a rigorous GEOMETRY course, just to name a few differences. Some of those things are pretty old school-- and the sheer volume, pace, and rigor in the course catches many students off guard, and always has.
It sounds to me like you're describing what is typically taught in precalculus. I'm teaching Algebra II right now and taking precalculus (in preparation for teaching it--or at least providing human-in-the-room help--next year) and am seeing a huge jump in complexity between them. But between Algebra I and II, not so much.
I also think what is considered to be a "huge jump in complexity" is dependent on the individual. None of these concepts were a huge jump in complexity for me as a high school student and so far haven't been for my ds, although I can see some that are causing him to think more than others. He's had some trig thrown in with his Algebra II course, and it was *easy* for him - the easiest (from his perspective) of anything he's done in Alg II. Not so easy for some of the other students in his class.
I also think it's important to keep in mind, as Mom2Two points out - having one challenging course doesn't mean everything from here on out is going to not work - I suspect that many of us had that one class in either high school or college that was totally completely unexpectedly difficult (compared to our expectations of smooth sailing because it was a class in a subject we were great at) and it was simply that - a class to get through, and once you'd moved on you'd move on.
I'm not saying this is the issue here - if dysgraphia or some other challenge is at play, it's not going to go away with this class. But if it's simply the material or the teacher or whatever things will be ok after this class is over. They'll be ok if it's dysgraphia or another LD too. The key is to understand what's up.
polarbear
