【正确答案】
I think it is reasonable to ask extra charges for extra training courses. Because training courses are outside the teaching syllabus of the school, teachers have the right to charge extra for the extra work they do. Students are not forced to take the courses. If they choose to enjoy the service, they must pay for it, just like they pay for other services.
It's true that some college students have financial problems so they can't afford the extra courses. But that shouldn't be a reason for denying that teachers should be paid for the work they do. If teachers are willing, they can give up the right to charge. On the other hand, they can insist on this right. Teachers are human and need to clothe, feed and shelter their families.
As to students who can't pay the fee, they could exchange services with teachers. For example, they might baby-sit for a teacher. Most students hope to pass the examinations, and to get the certificates that will help them find jobs. In this sense, at tending extra training classes is a vital investment in their future professions. How can one invest without paying? There is no free lunch anywhere.