Comment by realitygrill

As someone who wanted to redo my mathematical foundations and go onto higher maths, I tried (and failed) many different approaches. Eventually I found that New Math books worked for me. I'm about 70% through the www.elementsofmathematics.com course, which is derived from New Math, and loving it. Warning: it's about 3 years worth of work at a normal pace, and covers 6th-12th grade (through precalc, though you get some abstract algebra and number theory too).