You own the copyright to the assignments you have worked on yourself. You are entitled to make use of your previous works by, for example, using excerpts in later assignments. You just need to make sure that you have referenced them.
If you have worked on an assignment in cooperation with others, all co-authors need to give their permission to make use of the work.
If your lecturer would like to use your work as an example for other students by, for example, sharing it on Brightspace, this requires that you give your consent. Moreover, your name must also appear in connection with the published assignment.
For all assignments upon which you have worked yourself, you own the copyright. This is regardless of whether it is an essay, project, model, source code, thesis, etc. It cannot be made available without you having given your consent.
Some degree programmes at Aarhus University have created document repositories that contain examples of good papers which other students could benefit from reading. If you accept that your work can be uploaded to such a repository, you are thereby giving your consent for the assignment to be made publicly available. This requires particular attention from you with regard to copyright, as it is your responsibility to ensure that the contents of the assignment may actually be legally published.
If your work group has worked on joint notes, assignments or smaller text excerpts, which you have then made use of in another assignment, then you must also specify this in your assignment by making a reference to the source. If you, or others, would like to make use of the material that has been worked on jointly, all co-authors must give consent for it to be used in a new context.