entries 18 & 17 are interesting since it tries to convey the idea on how people will use the service by annotating videos, but I think this is too literal, to precise, and most people won't get it. The character style on entry 19 is better since it's more abstract. I realize that when trying to include a character most entries focus on a character doing some sports or activity, trying to represent a potential student. the problem is that coachzula applies to so many sports, that it may be confusing. Maybe you could think about using the character to represent a coach, rather than a student?
remember the Top Three Things to Communicate through my Logo: #1 - coaching #2 - sharing knowledge with community #3 - reaching new people (making money for coaches)