Scalable one-to-one tutoring is the most-cited promise of AI in education, and products such as Khanmigo have shown the shape of it. The harder part is not explaining a concept; it is declining to do the work for the student. A general model asked to solve a maths problem solves it. A tutor has to notice that the request is the homework, and respond with the next step a student can take themselves.
That behaviour is a policy, and the policy belongs to the teacher. How much help on a graded assignment, whether a worked example is allowed, when a hint becomes an answer: those vary by subject, by age and by school, so they are configured per course rather than baked into a prompt nobody can see.
The second problem is grounding. An AI maths tutor or AI language tutor that invents a method the class was not taught confuses more than it helps. Retrieval over the course material, with a citation on each explanation, keeps it inside what was taught and lets a teacher check any answer in one click.