I'm not sure what exactly what y'all are doing in terms of segregating newbies by skill - but it seems like there's still a lot of mixing true newbies with folks with a lot of UGC/pug/low-Open experience - I understand why but it probably is a little frustrating for a lot of coaches when a lot of players have really, really different needs for learning.
Some newbies don't know the names of locations or the utter basics of rollouts and advantages while others have the basics down but need to improve their gamesense or other aspects of the meta.
It might be good to segregate more stringently and have coaches take full groups of similar levels so everyone is equally engaged and make the coaching itself more rewarding - basically have coaches take all newbies or all advanced players.
Lots of times I played the coach wouldn't have much for half the team because they were so busy working on the utter basics with a player or two that they couldn't really offer much to the intermediate or advanced newbies.