Need Apple specific MDM advice for small (40ish) ipad deployment for school.

As per the title, our private school has 40 ipads that need an MDM to remove the headache of keeping them updated or applying settings across 40 devices.

The system - We're fully within the Apple environment on all devices. The ipads will never leave the premises, so we don't need remote access features. They don't hold any corporate security risk as they're strictly used by grade schoolers using education based apps.

The first major issue - We're not available for the ASM program since they only allow K-12 specific groups and we're an after-school program. We've asked multiple times, showed our license. Still denied.

The other issues - We're too small to eat the cost of $300 per month indefinitely of a professional MDM solution like JamF or Addigy just to update devices while they're charging at night. We don't need the cloud support that an MDM with remote devices might need, so we can't justify the price to parents. We're also too big for the free solution (25 device limit) for JamF.

What solution is out there or direction should I head in order to find something that will work for us? We'll have full physical access to the devices 24 hours a day. I consider myself computer literate, but lack any specific network or sysadmin professional experience. Thanks much for any replies.