When our son started nursery (okay 3 not 5 of school age), he could not pronounce his surname. (I'll admit it's a stupidly difficult surname, that colleagues struggle with on a daily basis!!)
He's known by an abbreviation of his long Christian name. So we explained to nursery that for writing we would like him to learn how to write his full Christian name, and understand the abbreviation, and that is what we would be doing at home with him.
We would say our surname, and get him used to the sound, but we didn't get him to write it, and he wasn't used to seeing it written down (as for example the labels on his peg and drawer at nursery were just first name same as all children).
He finally learnt to pronounce and write his surname by the end of reception.
But he could understand it if someone said it to him, from a young age.
This required concentrated effort by us, so can see if parents can't be bothered to do this and the child doesn't go to nursery how it can be a problem.