Mathworks does not make any copyright claim for anything you have written.
Copyright usually resides with the person who wrote the code, unless the program was a "work for hire" or there is some legal agreement otherwise. Assignments are not typically "works for hire" in law -- after all, you are more likely to have paid for the privilege of taking classes rather than they paying you. However, in some cases involving grants or scholarships, especially ones that involve the student doing something for the university (e.g., acting as tutor) then there is a possibility that "hire" could be construed even when working on assigments, in which case details of the finanical support agreement become important.
But in some universities (I do not know about Ryerson) there are terms in the student handbook such that officially assignments become the property of the university -- or since there have been court rulings against blanket assignment of copyright in such cases, the terms might say that the university is granted a non-exclusive license to use any work handed in for assignment.
If you ask universities, then they will say that those kinds of terms are just clarifying that they have a legal right to run the software for academic assessment (and plagiarism checking) -- and to be sure, if your prof were to nominate you for some kind of prize for good work, any examination of your work by the appropriate body would obviously be within the typical pervue of universities. It would obviously be academic nonsense for you to hand in work (thus fullfilling the terms of the assignment) but then to refuse the TA/prof/department permission to examine/run the code on copyright grounds.
... And although that is certainly true, that universties do need some legal rights in those regards, it is also the case that some universities have taken advantage of the wording on those kinds of agreements to copy and execute student code for other purposes, including licensing to commercial organizations, or including taking the work as the basis of research that the student is not notified of let alone asked to participate in. Keep in mind that it is common in research to take ideas that are not locked down by patent and develop the ideas without notification or permission -- and indeed, it is scientifically necessary that people be able to research and check ideas without permission, since it should not be possible for a person to prevent refutation of claims they have made by refusing anyone else permission to research the topic. So, talking about "permission" in a research context is sometimes murky or not obvious.
Anyhow: you need to read your particular university's handbook carefully to see if they discuss intellectual property rights. Which is a matter between you and the university, not between you and Mathworks.
With regards to how you establish copyright:
Unless provided otherwise in your legal agreement with your university, then any copyright you might own is yours as soon as you write a "sufficiently creative" work.
There is room for argument about whether code created for simple mass assignments is creative enough to qualify, since there may only be a small number of reasonable ways to express simple things (you don't want later students to have to submit their code through a checker that checks every single previous answer, not for potential plaigiarism but rather just for sufficient "creativity" for copyright purposes. The clear good ways of writing the assignment would get "used up", pushing later students to worse and worse code.)
But that is a consideration that is not going to apply to what you are talking about: you have created non-trivial code for which copyright would automatically apply.
When I talk about automatic copyright, I refer to in countries that are subject to the Berne Convention on Copyright or one of the later similar treaties. That does apply to Canada but there are some countries which have not signed. Automatic copyright by the author of the work has been the mainstream for decades; countries that do not have that require specialized country-specific advice.
Provided that there is nothing contrary in your agreement with you university, you would indeed be entitled to place your work under one of the Creative Commons or Gnu or BSD or similar licenses, and you could use the appropriate logo in accordance with the authorizations set out by the creators / owners of the relevant logo.
