The student typically spends most of his/her time with students of the same level of ability or interest. For the student who will someday become a college teacher, this general means able and interested students.
The teacher spends time with and on anyone who signs up. For the intro classes at least this will include a proportion of those who are neither interested nor able.
In my opinion typically they are informed about the wrong things (and also sometimes in a wrong way). Yes, I grow old. :-)