How to grant some (!) devices access to network but all others have to provide passwords

[uj2.hahn at posteo.de]

Hi, all!
I'm pretty sure this is a very basic question which might have been 
discussed in the past already.
But I'm new in this area so you might apologize this silly question....

In a school all devices (students laptops, mobiles, tablets) have to use 
username/password via Freeradius
to get access to WLAN. But there are some well-defined school-owned 
devices (laptops, tablets)  which should
connect to WLAN  immediately w/o any credentials.
Which options do I have to realize that? MAC checks? Certificates?

Thanks for your help
Uwe