Why do I have to see a grief counselor?

The grief counsellor can give you instruction on the etiquette of grieving for people you did not know or care about.  They can show you how to set about tying flowers to fences and railings, and how to write a suitable epitaph on a bit of cardboard with a sharpie.

All you need to do is tell the counselor when you go for your appointment that you never knew the kid in question. You should be allowed to return to class in that case. It's what any normal person would do. NO, you aren't required to grieve for someone you never knew- in fact, it would be impossible for most people to do so. But your school's administration doesn't know how many friends among the student body that this person had, or who those friends were. THAT is why they are making the initial grief counseling meeting mandatory, so that they can figure out who they really need to talk to and who may need help to come to terms with this.

MOST schools will make grief counseling available to students when someone dies or is killed. It's a state requirement in most places. If you never knew the person, that's all you have to say to anyone.

Some students will have a reaction to a death, even though they didn’t know the person.  

Just tell the counselor what you wrote here when you have your meeting. Go and get it done with instead of whining about it.

your meeting should take about 2 minutes, tops.  just do it and then forget it

They probably just want to make sure everyone is okay. Some students might feel more anxiety or sadness than you do, but are afraid to come forward voluntarily. Making it mandatory means that everyone who needs help will get help, without putting the burden on them to come forward.