Hi Chris,
Firstly to agree with Simon, The capabilities of any solution for device management are indeed governed by the OS manufacturer and the release of the relevant APis to MDM vendorworld.
Apple configurator is a great tool for the initial set up of a low number of devices and moderately proficient at ongoing management if you have the time, resources and visibility of the devices on a regular basis. The issues you have are clearly outlined and as you describe them make any solution that relies on physical connectivity to provide the management function for over a hundred devices would be a short walk to near insanity for you.
I would suggest a solution designed around a full "multi tenancy" hierarchy, AD integration, secure email gateway, proxy filtering etc etc. This is the fundamental technology underlying the Airwatch solution. Allowing each class to be provisioned according to age, subject, need, month, day etc etc in real time by the classroom manager (teacher, LA) is key to what you are tasked with achieving. Recommend you examine the capabilities of each MDM as to their multi tenancy depth especially as you are potentially looking to manage a variety of end users over a variety of sites.
The most cost effective solution would be one which allows full real time over the air management of those devices at a level of granularity which allows you address the specific requirements of each of the schools you mention. There are a plethora of cost models out there from Standard subscription to perpetual FTE and all things in between from various vendors. I would be happy to discuss further.
John