nbgrader has a concept of a solution cell. Does nbgrader solve for some of these use cases?
https://nbgrader.readthedocs.io/en/stable/contributor_guide/metadata.html
If you’re writing tests for students to write code to make pass, those assertions should fail when executing the notebook. (assert, ipytest, nbval) Are students then expected to change the cell back to a code cell so that the code in the notebook runs?
You can also change the cell type to raw, but that lacks syntax highlighting and also requires an annoying extra step to run all of the code in the notebook.