I work, part time, at a very multicultural school, and my youngest is currently in reception there. Over half the class are non English native speakers and over 3/4 of their children had no English when starting. These children come from India, Pakistan, Italy, Russia and Romania. Two mums I know, have only spoken English to them, since they were born (other family speaks native language).
Can you imagine having 10 children, in a class of 30 4 year olds who don't know how to ask to go to the toilet, say they're hungry, or explain how they're feeling? The way the school handles is is amazing. One thing they do is use picture folders for the kids to point at, which are really helpful, and a term in all the children have a basic grasp of the important language. That being said, they're not a language school, and for those 10, there are 20 other children who already understand English, so have other needs. The poor reception teacher has to take ALL those children and get them to a certain level for starting year 1 (which is INTENSE!) whilst fostering each individual child's separate needs, likes and talents, to give them all an equal teaching experience.
I've found that my child's teacher actually spends a lot of extra time talking to the parents where English isn't their native language, as they need to be explained things multiple times (hair needs to be tied back; costume needed for play; He didn't have a coat today; packed lunch was unsuitable, dangly earrings aren't allowed).....all things that are very simple requests I've heard whilst waiting for my child to be let out, but seem to have to be said every day, because the parent smiles, nods and walks off not understanding [possible embarrassment?] , so the teacher has to repeat it daily, trying to make it understood). I can't imagine how stressful it is for them. Yelling at your son to come to you, when he's listening to the teacher is completely unacceptable. Just wait your turn.