Every school in England that follows the National Curriculum has to assess each child in their speaking and listening skills at key stage 2 and 3.
The way we speak greatly influences the way other people treat us. If we mumble and use lazy speech we give the impression that we don't care. If we speak clearly so that people can hear us, we tend to get treated with more respect.
This applies to children at school with teachers as well as outside of school with shop keepers, dance teachers, soccer coaches etc.
It's a fact of life that any child who has good clear speech has a head start in life!
Most people think that they can listen without having to be taught how to do it. However there are different ways of listening and they are discussed here.