I don't know about teachers in Wales, but where I work the teachers are much too busy teaching to play silly mind games. The most likely explanation is that your child's teacher overlooked, or misplaced your child's work. If any of my childern's teachers had ever refused to discuss my child's progress after I asked about it, then that teacher would not still be teaching. So, just ask the teacher for a conference about your child's progress. I think your fears about mind-game conspiracies will be put to rest.