There are a number of reasons players will move. We spend a lot of money to join these clubs. What if: 1: they don't see much playing time 2: aren't developing under current coaches 3: is an "A" type player playing in the B league 4: chose current team due to geographic location and will now travel further to play on a competitive team . I'm sure there are many other reasons.
We plan to have our DD try out for several of the top teams this mainly due to Reasons 2 and 3. I'd add for # 2, it's not only just coaches per say but overall development within the club etc but they go hand in hand. 2 and 3 I think are the top reasons why you will see a lot of movement to the top teams.
I'd be curious to see about # 1. Do players on the "A" teams of the top teams who aren't playing much stay with the club and move to their B teams or do they go to other A clubs that aren't as competitive etc? CClax will be in A next year with their win and I could see a few of the current A teams dropping back down to the B division, i.e. Limelight, Stars and maybe even Skywalkers.
Its rare for a team to move backwards in divisions. remember typically there are 10-12 A teams in 6th grade, 14-16 in 7th grade and 18-20 in 8th grade.
For girls on A+ teams, you will see some girls tryout for A teams where they can play more or play in a preferred position. You will see stars on A teams try out for A+ teams and B players tryout for A and A+ teams.
Also, remember some girls will want to switch team for reasons beyond lacrosse. Lots of cliques on 6th and 7th grade and this can break teams up.
Biggest X factor around this age is how many girls drop travel lax all together due to committments to other sports (typically soccer).
Remember though that between the top 4 teams, there are usually only around 15-20 spots which open up.
For reference last year at the 27 level for the top 3 programs)
M&D added 3 new girls (but cut 6 or 7 due to having an inflated roster due to having a Red team collapse at last second)
Heros added 5 girls (including 1 from White team and 1 from out of state)
BLC added 3 new girls.