Indeed - if this became commonplace, a public school that wanted to keep the riffraff out could find all manner of "critical" materials that all students would be required to purchase. This could be similar to the poll taxes that used to be used to keep the poor from voting. The fact that there are school assets available "during the day" for students to use is somewhat relevant, but you and I both know that there will not be enough to go around, there will be severe restrictions on use (and I'm not talking about web restrictions - I'm talking about file storage, functionality lockouts, etc) that will inhibit the value of the asset to the student.
No matter how you slice it, this will create a very uneven playing field using an arbitrary financial discriminator.
If it were required for a particular elective class or a class for which there was a non-computer-required equivalent, that would be completely different. It would be less ridiculous to require high school students to purchase their own textbooks - and we know how that would go over.