Sorry for being long-winded, but let me see if I can explain a little. I can't seem to just keep is short and sweet
Please keep in mind that this is just a parent perspective of what is happening based on what I see and what the coaches tell us. I really know nothing.
Generally the girls in each group are working somewhat the same skills. They adjust what is being asked for each individual girl. Each gymnast has their strengths and weaknesses and some girls are working farther ahead in one thing and not so much in another. They are really allowed to push their strengths and given the time to work out and build upon their weaknesses.
In general I have seen no issue with the difference in level as the philosophy is that all the girls should be training skills 1-2 levels up and compete where they can be successful. Competition at compulsory levels is for experience and confidence. The overall goal for everyone is high level successful optional gymnastics and hopefully college scholarships. Some will get there and some will not, but that is the goal for everyone.
An example, we had a girl who did three years of level 4 because she couldn't hold it together in competition. She would just fall apart. But then the third year it finally clicked for her and she did very well, even winning AA several times. But she has been training higher skills and has stayed with the girls who train at her skill level that whole time and it is possible that she will compete 6 or even 7 this year, just scoring out of the others. Watching her train, she looks totally ready for that.
In my daughters group they are all working toward competing level 5 this year. Some of them will compete five and some will do another year of 4 depending on what the coach feels is best for the gymnast. Some may need another year of level 4 for confidence or because they struggle with a skill or two and need more time to polish. Some may be ready after another level 4 meet or two and move to 5 mid season. Some are ready to compete level 5 right now.
Really there aren't any rules, the coaches train how they feel is best for each girl. The ambiguity has been tough for some parents and the program is definitely not for everyone. I really think it is great. My dd is one who may benefit from another year competing level 4 for a variety of reasons, but I am very reassured by the fact that if she isn't ready to compete five she will continue to work her level 5 skills and start training level 6 skills as soon as she is ready. And she will get to stay with the group of girls that she is bonded with and support her. They are amazing friends and encourage one another and are as excited about each other's successes as they are about their own.
If a girl becomes too far ahead or behind, I would have to assume they would move her to an appropriate work group, but I haven't seen this happen much.
During competition season they are still uptraining and working new skills along with working their routines.
examples of how a practice rotation may go.
So on tumbling, there may be several fundamentals stations with conditioning in between and then each will take a turn on the tramp, but one may do a back handspring and one a front or back tuck depending on what skill the coach is working with them on. The when they get a turn with the coach then they will do whatever skill each kid is working on that day. One may do a ROBHS and another may do a ROBHSBHS and another may do a ROBHSBT depending on her skill level is. The coach is always watching everyone and will make adjustments when needed on each station. It's like they have eyes everywhere (amazing).
On beam is looks like there is something they all work on and then the quicker you master it, the quicker you get to move on to uptraining whatever it is you are working on at the time. So they may be doing vertical handstands as a group and then once a girl gets good ones and can show the coach then then they can move onto working on their cartwheels or backwalkovers depending on where they are.
Floor routines get a little more complicated, but they make it work by breaking the group up into smaller groups. We have enough coaching coverage (about 6-7 to 1) to ensure that everyone is safely watched and given the individual attention she needs to be successful in this system.
Overall, it is awesome. I couldn't be more confident my dd is in the right place. That doesn't mean I don't have my frustrations, of course, but overall I am very pleased.