4th year 3rd string

as a single mom when my kids were little i didn't have time, or make time to teach my kids the basics.
therefore as an 11 year old and 4th year player, my kid is still in 3rd string.
I play with him now and encourage their step dad to help, but I think I'm on my own.
short of powder puff football in highschool. I lack a lot of the information that I need to help him.
I have tried to teach what I thought was common sense football and i guess it's just not enough.
My defensiveness says that after 4 years the coaches should be able to take anyone and turn them into an ok football player.
But i know he's off to a slow start. I need to be able to learn the game quick so that I can see what he is doing wrong at practice and help.
Please send any direction or encouragement my way.
It is heart breaking to see in on the sidelines ------ still.