This is ridiculous and pc has nothing to do with it. You can't blame muslims for teachers being cowards. At some point, people have to stand up and take responsibility for what they do. It shouldn't matter to a history teacher what a child is taught outside of the classroom. The teacher's responsibility is teaching accurate, important information in the classroom. You can't possibly teach history and leave out world war two and you can't teach about that without discussing the holocaust.
BTW, there already is a Holocaust memorial day in the UK. It is on January 27th, which marks the anniversary of the liberation of Auschwitz by Soviet troops in 1945. Of course, the muslim council of Britain opposes it saying that the victims of the Holocaust shouldn't receive special attention. They've suggested replacing it with a genocide day to remember all victims of genocide. The Armenians complained about it too cause they don't have a special day. The problem I have with them is that they act like the Holocaust was only killing Jews. It wasn't. Slavs, communists, homosexuals, clergy, union activists, gypsies, the physically and mentally disabled... the list of those killed is much longer. Commemorating that event in history isn't about giving Jews special treatment. It's a tool to discuss genocide, racism, bigotry and human rights in general. I can't see why anyone would oppose that because they are still relevant issues today, as we've seen in Rwanda, Bosnia, etc.