The girls I work with in these levels love contests. We do a lot of contests, stressing sportsmanship and effort, but we also do call out a winner. We do enough contests that everyone wins sometimes. I know our girls love these b/c they ask to do them regularly. Some of the contests we do are:
-HS, winner is the one who held it the longest AND came down correctly w/ arms by ears.
-HS roll, winner is the one who held it the longest and successfully rolled down.
-HS bridge, same as above, longest who landed in a bridge
The winner(s) move to another spot and keep practicing while the other girls continue the contest.
We also do a lot of "points" contests. Pick a skill you want to work at that level, say bridge kickover. The girls get 1 point if they can kick it over, 2 points if the legs are basically straight, 3 points if the legs are straight, toes pointed, arms by ears when they finish, and 10 points if it makes you so happy you want to continuing teaching levels 2 and 3. We either count all the points together as a group and when we get to whatever # I picked we get to do 5 min. of trampoline, or any reward you choose. The other way we do it is 2 teams and the first team to x points gets a reward, or chooses the reward that the whole group gets.
It sounds simple but we have found contests to be very motivating at these levels as long as you stay in charge and nip any sportsmanship issues right away.
You may be surprised how much extra effort you will get from the girls with even very small rewards at stake. Be creative about your rewards, it doesn't have to be time consuming. When our girls were struggling with rope climb we let whoever made it to the top of the rope yell out "I'm the strongest girl in the room!" and then the next one to make it got to yell "NO! I'M the strongest girl in the room!"
One other thing we do with these levels is when they start to fade out we tell them that obviously they are very tired and need a nap and have them lay down and close their eyes until the alarm goes off. We use this sometimes if the coach needs to use the restroom, they can nap for another coach or on the carpet outside the bathroom door (whatever works right?) After a few seconds ... ding, ding, ding, time to get up! Silly I know but it works for that age group. (Thanks to whoever I stole that from along the way.)
Good Luck!