STUDENTS TRAINING: What influence how fast a student will become student (debt)?

So, from what I've read following things ifluence how quick a student becomes a student (debt):

• how "old" is the Student card, "older" Student cards have a higher chance of becoming a student (debt),
• number of University Campuses in the city,

• Numbers of Professor cards in the city.

My questions:

1. Are there any other things that influence how fast a student becomes a student (debt)? Do Teacher card or University card also help?
2. How many University Campuses I need to have to have 100% probability of a student becoming a student (debt)? How much does a single University Campus card increase the probability?
3. Same with professors - How much Professor cards is needed to have 100% probability? And how much does single Professor card increase this probability?

Thank you in advance.