I second HowlerKarma's thoughts on gaps after doing EDM. My DD had some really weird ways of thinking through math after doing EDM for 3 years. Sometimes her methods were due to RDM and other times it was because she had developed her own way of doing things which don't always work when you get to algebra and beyond. She didn't even know she didn't understand things until we would sit with her and have her explain the method she had used and why she thought it would work and then we'd have to show her how it was wrong and what the correct way of doing it was. We had some tough days because of it, but it only took about 4 months to undo 3 years of bad math foundations, so I guess it wasn't too bad.
