For the last two days I have been trying to think of training reserved for adults, and I can't think of one.
Adults can complete their school education (O-levels and A-levels) at evening classes. Universities and colleges are, I believe, open equally to adults and students. But often the study undertaken by adults is specific to the career, not age. For example, teacher training college, nursing studies. Engineers take the exams to be part of, for example, the Electrical Engineers Institute, accountants study for the membership exams of the Institute of Chartered Accountants, or of Cost and Management Accountants,etc.