MLA has been standard here but I've been moving my Science and Health classes to APA with AOK from the teachers. With Databases and Noodletools, it's the click of a few buttons, at least for References at the end. I show them both MLA and APA citations, side by side and have them detect the differences. Brief discussion on why date is more significant for sciences, etc. Should reduce some shock when they get to college, where professors will be asking for all sorts of citations.