They legally HAVE to accomdate your health needs.
You should have an IEP or 504. It should say something about missing class. I got notetakers and no penalty for missed classes/tests as long as i got a note. You can also get out of gym if it's in your IEP.
If you were in the hosptial, most of them provide a homebound/tutoring program or something. Ask, and get your social worker to talk to your school.
I just graduated, and i did fine.