I spent time in the 90's working with a junior only development team. It had a track focus, but junior distances are so short on the road that the training overlaps well. We had a kid as a 14 year old, took all the national champions jerseys for both the road and track. He did a 12.1 200 meter time, which would have qualified him for senior narionals. He rode an 84 inch gear. That was the gear he liked. Kept up with cat 1/2 fields. In his time as a junior, he won maybe 15 plus national champions jerseys and a top 15 at worlds on the road. The coach was very into developing cadence. All his riders were like that. Another one of his riders got 3rd at nats road by soloing off the front of the field on the start of the last lap. He went on to ride for Marion College. He was also competitive in the 1/2 fields. He won me a gift certificate to the Mac and Jack brewery because he was only 17. I got to him before his Dad did. I think it is important to start developing cadence early. As a young rider matures, they will develop the strength to ride larger gears, hopefully still retaining their ability to pedal fast.