What do you do when you feel the teaching at your child's school is below standard?

For some time I have been worried, My daughter is in reception and so fluent in english. Recently there was a school play and I felt the way the children were given roles wasnot fair, it seems the children whose parents were actively involved in school activities had their children given good roles yet the way some children spoke was not even audible. This is not the 1st time I have been bothered by this. How can I complain about such issues without causing friction and avoid victimisation of my child. how do I take up this issue. The problem is some children(including mine) are not getting the same level of attention and are simplynot given anything challenging. How can I handle this?