Can an iOS device be managed by more than one MDM platform?

The answer is no, as you already surmised. This isn't a Casper or other MDM thing, its an Apple restriction.

Do you know more about the kind of things this parent would like to be able to do?

I know that the Zuludesk MDM (targeted at schools) has a feature that parents can set other restrictions at home than at school, including app restriction and time limits. The key is either time (after 17.00) or location (not in range of school wifi).
So managed by one MDM, but with two different restrictions for two different situations!
https://zuludesk.com/features/zuludesk-parent/

Ask jamf to implement something similar in 'feature requests'

What exactly is the parent trying to do? Why aren't Restrictions good enough?

I've read up on Curbi and they have a VPN app that is filtered if the school is already using MDM. Student has to agree enough to not remove it..

It's just a user-friendly app for parents to control the iPads - disable use, disable internet, disable apps, etc. Doesn't work if the iPad is already MDM managed, we tried.

@cdenesha: the 'parent thing' portion of zuludesk is designed for this scenario:

iPad used for school material for kids, either property from school or BYOD.
During school hours (or school wifi) school manages the iPad: only school apps, no facebook, whatsapp, etc
Out of school the iPad can do what the parents decide: -(almost) no limits
-or set time limits, restricted apps etc.

See the link for example screenshots

I know that the parent settings has been a good 'tool' to overcome parent's worries over too much internet/social activities of their childeren. And if the parents have to pay a (part) of the iPad, this can be a good thing when a school tries to modernize.

Call me crazy but.... while there would be some conditions I'd put in place -- there is nothing preventing using Casper Focus for parental use. You could create a class (parent access) with just the parents children and limit the times to the appropriate period -such as 5pm to 6am.

It would add a layer of IT support; however, in my last district we had several "parental" portals the we supported. A required parent training could counter "usability" concerns.

Send a message to come down to dinner
Restrict to iBooks at bedtime
Restrict to a single website for LMS access.

Sure some parents would "forget" to unfocused their child -but likely that would only happen once as the child wouldn't remind them.

I've read up on Curbi and they have a VPN app that is filtered if the school is already using MDM. Student has to agree enough to not remove it..

We had a few parents using Curbi last year, but as of this year they've dropped support for devices that are already on another MDM.

All of the other options I found in the app store require a profile, which won't work for us.

Does anyone know of any other options for parental supervision that exist right now? The parent requests these features:
- Limit use of distracting apps during homework time and when the parents are at work.
- Track time spent on homework.