Wow things have really changed since my son played soccer. Once the kids were placed on a team they stayed on that team unless they chose to leave.
I coached his team one season when there was no one else to do so, it was quite the learning experience. We actually did fairly well as we had most of the team returning. I was given decent training to top off the fact I had been working for several years with the other coach.
It was at this point that the teams were going to "premier teams" and I saw some of the bullshit your experiencing. My son takes after me therefore is very small . He is only 5'6" as an adult. Back then he was much smaller than the other boys even though he was a year older than a lot of them in his grade. He was passed over by the premier teams just on that factor even though he could outrun most of the boys 2 or 3 years older than him. All people see is the need to win, doesn't matter what they are saying to the kids.
I am sure you will succeed with what ever team you work with, because you care about each individual
. Whether you win or lose, your still winners.