My 2 cents on a couple more things for younger GKs...
I'll add that I think coaches and parents make a big mistake allocating younger kids as full-time GKs too early. My advice is that kids should continue to get as much field time and work on skills as much as possible. Thus, splitting is a good thing as long as field time is involved. Don't go full-time in the box until its clear that the kid has a future at that position. My rule/advice is that before puberty use the Khamis-Roche Method to ascertain whether the kid has a decent chance at continuing in the position based on the following standard:
- Girls - Tracking above 5'7" (average height of D1 is 5'9")
- Boys - Tracking above 5'11"
I've seen multiple female soccer player absolutely ruined because they went between the sticks full-time too early. They loved soccer, were great U10 field players, became full-time GKs and slowly become mediocre field players by U14, then by U16 had no team that wanted them for the field or keeper at 5'4" (average woman's height). Those shorter keepers get relegated to the C team and/or the bench until after the game is decided.
Full disclosure: My son was 5'9" at age 12/13 and is now slightly under 6'2" at age 14. He was always tracking 6'1"+, so I was OK with him becoming a full-time keeper at the U13 level, but he still split time on the field on his U14 team because he was one of the top field players and the team needed field players. Last year was his first year as a full-time keeper and he played up a year.