In some universities, students are allowed to choose their courses's professors freely. Students usually choose the teacher according to their interests. Some students prefer to make a choice to the lecturer who is kind or who is easy to get alone with. Maybe the main factor is which teacher allowed them to make it easy to get a high grade.
    In my eyes, everything has a positive side and a negative side. The positive side is that they may learn the course better, because they may choose the professor they liked. The negative side is if the professor who is very popular and a host of students would like to attend his/her course, the classroom must be crowed. It may cause a bad impact about the class.