While many answers here outline potential dangers arising from giving someone admin access, it should also be noted that it's also a reasonable tool for the job the school IT is about to do. That's what I would request from parents if I were to do it, since explaining how to properly configure their own system would be a dead end. 80% of them wouldn't even know what a certificate is.
It's true that admin rights can be easily abused, but assuming you trust your school, I wouldn't worry about it too much. Think of it this way: you're asking yourself whether those guys will abuse their access to a laptop, but you have no problem leaving you kid with them for the whole day, every day. Are you sure the laptop is the thing you need to worry about here?
Incidentally, even if you choose to educate school IT about better practices, their Outlook licenses won't transform into Linux seminars for teachers. I agree that it's a noble cause to fight for, but in your situation it's far too late to actually change anything.