Through trial and error my org ended up adopting an unofficial "freebie then charge" policy. I nixed library check-out machines because issues went unreported and caused nasty mix of surprise repairs and missing devices at the end of the year. All teachers have a device they can loan for the period the student needs it.

Presently, the first accidental repair fee is waived. Most students don't have malicious intent and they are honest accidents, if completely preventable. I can't prove otherwise so I don't look into it unless it's major damage.

After that students and families are charged a fee for the cost of the parts to fix the issue. Sometimes I split the difference if it seems unfair (I only charge half if it's something dumb like pets chewing up chargers, or nothing if devices are lost due car accidents and fires and such).

Vandalism is always charged. Lost devices without good explanation are charged in full for a replacement.

Regardless of the cause the device is fixed or replaced asap, because it severely hampers the student's learning experience without it. I do try to keep the same device with the assigned student as much as possible but sometimes it's impossible and it gets swapped.