We have an iPad 4 from 2012 that runs on IOS 10.3.3, It seems to accept some commands from JamF School but most of the the command's we can send to our newer iPads do not work on this (e.g. it won't accept a background image or a webclip). It also says it's 'not supervised' although we did install it through AC2. Is this due to the iPad being old and the IOS is old or are we missing a step here?
Did you import the supervision identity from Jamf School into AC2 or are you relying on AC2 alone to provide the supervision? Here is the documentation for importing a supervision identity just in case.
According to Apple's documentation setting a wallpaper for instance is possible on iOS 8 and higher but you need to be properly supervised.
We ran into similar situations. Jamf can't support all functions indefinitely on all version of iOS, iPadOS, tvOS, and macOS. I know it isn't a super helpful answer, but you are kind of stuck in that position. The only real way to support the user, is to update the device.
iOS 11 and older listed as untested on the current version: https://docs.jamf.com/jamf-school/documentation/Jamf_School_System_Requirements.html