in most of the countries the drop out age of student is 18 years. i believe this age should not be raised because allowing the students of greater age sit in the class will make it difficult for them and the rest of the students. they will feel alone because rest of the students will be of average age and they might not be able to make friend. the other students in class of the average age will not be comfortable to blend with the student who is elder to them in age. it might create difficulties for the teacher as well because they will have to deliver the lecture for two different mind levels sitting in the class.