[MarcScott]

Almost every school in my area (UK) uses fingerprint scanners, including my son's. They're used only for purchasing food from the school's cafeteria.

I'm quite "privacy aware" and don't really have any problems with this. The schools act under GDPR, the data stored is just a hash of the fingerprint, and compared to the data held on the school management software, a fingerprint hash is pretty negligible.

My kid could pay in cash, but that introduces the possibility of losing it or having it stolen. They could use an ID card, which again can be lost and would still end up storing data.

[knz]

My kid's elementary school in the US uses their initials and a five digit PIN.

It took about a week for them to learn their PIN (during which time they had a card with the number) when they started school but, several years later, it works fine and doesn't involve exposing their biometric or other PII data.

[rwmurrayVT]

We used 7 digit code that was assigned to us. It stayed with you K-12. You could 'prepay' for your meals with a single check. I did that until one day the entire school found out my number was 1008000. Suddenly, I had no money to buy lunch and a large amount of library fines. They couldn't change my number so my parents were forced to give me 2 dollars every day and I knew the librarians very well.