My old schools and my current college work on an Attendance system.
At the schools, if you've got an attendance rating lower than 95%, then you're in trouble and have warnings.
If you miss lessons without them being signed out by a parent (calling in sick) then you're likely in detention and have a warning (for truancy).
If you're consistently off, I think they expect to have a Doctor's note to explain the reasons.
At College, if you have an attendance lower than 80% in any lessons, then you'll get warnings and be put onto contracts.
Basically saying that if you don't start turning up, then you can be kicked out from college (even if you're only missing something like tutor [Not a subject] but going to all your actual courses).
Since theattendance at College is entirely optional and up to you, they have a different method for signing out.
I can go onto my College website, log in, and report an absence for a large number of reasons. Illness, funerals, medical appointments, having to care for a child or loved one, job interviews, etc...
This is all fine, and using it is acceptable, but if overused (and attendance rating slips) you get in trouble.
If you're constantly signing yourself out as sick, you'll require a doctor's note to explain why you're so frequently sick.
Missing lessons without signing out is quickly asking to get in trouble and be put on contract or expelled.
