Greenmonsters
Wannabe Duck Boat Owner
Absolutely! I know some players will have a lighter bat in their bag to use against faster pitchers because all things being equal the same player will usually generate more bat speed with the lighter bat. I had one player who was a decent gap hitter who loved to swing a lighter bat because she had better bat speed with it and she claimed she could wait an instant longer before committing to the swing and it helped her make more solid contact. I can't argue with her results. Other girls want to swing the heaviest bat they can comfortably swing. One thing that I think is almost universal is that if a kid is hitting well nobody messes with anything. If a kid is struggling, we want to questions her mechanics, her bat, what she ate for lunch, etc...
Here's the problem, good results don't necessarily mean good mechanics and that is the crux of the problem with light bats IMO/IME. In fact, it often is the case that it isn't until the quality of pitching increases that the poor mechanics previously masked by light bats are exposed as successful at bats diminish significantly. With the long-term in mind i.e., the goal of playing at some collegiate level, there really should be a much greater focus on the mechanics than the results at the younger age as the longer poor mechanics are utilized and ingrained, the longer and harder it is to correct them.
In my case, it was the summer after finishing 8th grade that DD decided that she wanted to get more serious and try to play in college. At that time I explained that although she was one of the better hitters in her local peer group, we needed to break down and rebuild her swing mechanics if she wanted to a chance to play, not sit the bench, at the next level, even if she was only interested in D3 schools. She bought in and we steepened and shortened the learning curve by working exclusively with a heavy, end-loaded Rocketech during during fall and winter "off-season" practices and games. There was a minor step backwards for a frustrating (but relatively short) period of time, but the new mechanics were ingrained in time for her to be the only freshman starting HS varsity come the following spring and subsequently served her well during her college career. YMMV.