We haven't managed to keep FLL teams around in our elementary schools long enough to be much of a feeder system. Once the kids move on, the parents leave, and those parents were the mentors. It's very hard to find parents who want to give up their time to mentor the teams, and without experienced mentors the teams have a ton of trouble - especially in Michigan's ridiculously compressed FLL season.
We have no FTC teams because of the overlap between the FLL and FTC programs. Frankly, FIRST needs to wake up on that score - if they want FTC to succeed they need to lower the maximum age of FLL so kids are forced to move over. That's a different post though
.