Daniel recommends you use a number column and put the ID in that column. In fact, he would name it ProfessorID
The other option is to make it a lookup column.
The side effect is that the column would then contain an object the could have both the professor ID and name. The downside is that patching is somewhat trickier. I have not tried patching a lookup object, but I've been told it can be done. From a PA point of view, I suspect either would work, and from the SP list point of view, you can see the professor's name.
The next issue is if you want to link to a student's table. There is only one professor per class, so it is pretty easy. There could be fifty students per class, and lookup would possibly work too, but even in SharePoint, it would look awkward.
Take option 1 (link on a field). It does not have to be ID, as long as it is in both list and matches. LookUp columns are a bad idea to link to Power Apps unless you cannot avoid them with your required structure. I have a blog relating to field types if it interests you.
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