Is it permissible for a teacher to profit from selling summaries and reviews that she prepares for students?

There is no objection to a teacher preparing notes, summaries, and revisions that benefit students, and selling them to them for a profit, as long as this does not conflict with the educational system and the sale is based on mutual consent. Buying and selling from distinguished students is permissible if their guardians have given permission; otherwise, it depends on the guardians' endorsement.