Either get in touch with the school you went to or one near where you now live. All teachers are overjoyed when they find out someone wants to 'join' their clan! Simply ring up the reception, explain that you want to do a work placement before starting your course and they'll probably already have a system in place for arranging this. Don't worry about the police checks etc - the school will know all about what procedures they will have to go through and will guide you through. Good luck!