How long do you think that Apple should support a device for? I agree that two years is pretty short, but some of the technical limitations make it hard to place too much blame on Apple.
Two years is a pretty short cycle for replacing an entire district's supply of iPads. I would guess schools that bought sets of iPads were not told that they would likely be obsolete in two years. You can say "buyer beware", but I think salespeople have an ethical responsibility to paint a realistic picture of what they are selling to schools. Salespeople should probably act, in part, as technical advisers to their purchasing contacts in school systems.