Hi Michl, unfortunately, my son tried that route and I found out first-hand. It never occurred to me to go to the website. Methuselah, smart move! Don't know if I was lazy or emotional but I called the school counselor and she set up a mtng with-me, my son, and the truancy officer.
B4 that, my son was hauled into the principal's office by my landscaper while I was out of town (I do not suggest that you go this route, it is rather circuitous, lol!).
The school will have a set # of days from which the student can be excused. Past that (in our middle school, it's 7) they call in a truancy officer and try to get a lid on the problem. If the officer sees real trouble, he or she can immediately place the child in juvenile detention, where they have classes and lockdown units.
If the officer thinks it's something else, s/he can call the parents and arrange rides, escorts or whatever. It depends upon the kid and his attitude.
I would call the school counselor and/or the asst principal or whomever you are comfortable with. And yes, you can look up some of it on the web, but I'd rather share my problem and get my kid's name out there among staffers as much as possible.