If the solutions have been copied from a set of solutions published by the university, they will have copyright. If the solutions are the students own work, then they won't, and this is abuse of the DMCA.
For the sake of a mind game assume that assignments and solutions can be copyrighted.
The mind game is: The assignment is most likely produced with a solution, but published without (lets say else it would not be 'assignable'). For deterministic solutions, could you copyright it without publication?
The mind game is: The assignment is most likely produced with a solution, but published without (lets say else it would not be 'assignable'). For deterministic solutions, could you copyright it without publication?