Chaps

Growing up I always wanted my own pair of chaps. My dad never went riding without his and in my mind they were what made you a real cowboy. Until my son was in Fourth Grade I'd only ever heard that word pronounced /sh/aps - like shag. But then his teacher pronounced it /ch/aps - like it is spelled - like when your lips are dry. He tried correcting her and she told him he was wrong. Well, no one told my son that his knowledge of cowboying was wrong, so he had me go talk to her. I set her straight in a very gentle and diplomatic way - by telling her that's how my dad always said it. Since then I've heard other actual cowboys pronounce it the same way she did. So now I'm curious... is it a tomayto/tomahto kind of thing? Or is someone out there saying it wrong?