I had B and then switched to E. But I understand why E is wrong now. E is just bringing outside information that is not mentioned in the argument doesn't do anything to weaken or strengthen it. B attacks explicitly the argument that is outlined, which is: Participation -> Performance Increase. "some students doing well that didn't participate in the program" does not provide any reasoning as to what's wrong with the phenomenon. B saying "most of the students parents were experienced teachers" is stronger in attacking the argument because it's saying "ok all these kids parents are already teachers so of course this sample of kids is going to do really well"

5/5 on medium. The longest I took was 2:03 mins on number 4.