I'll chime in here that my spouse and I (both scientists with terminal degrees and former Uni educators) love Singapore Math's approach to teaching elementary mathematics.
Seriously-- this is pedagogically the best thing going IMO. It teaches kids applied mathematics right from the get-go, setting them up perfectly to use math as a tool in physics, chemistry, biology, economics, and engineering disciplines later on. No drill-and-kill here, and it teaches terrific algebraic problem-solving skills in holistic way throughout the curriculum. LOVE that.
We used Primary Mathematics with our DD up to level 4 (I think)... both textbook and workbook (I'd have her do only ~ 1/4th of the problems and leave it at that if she had mastery), and also the CWP workbooks. She used to really look forward to doing the CWP problems. I used to use them as bribes to do the textbook/workbook material.
Nothing that our public schools are using even compares; this is my one serious, lasting regret about going to a public charter school. <sniff-sniff> Five years later and this is the first year that my daughter is actually excited about math again (honors geometry).
It's just a nice bonus that Singapore is inexpensive. A year's worth of materials used to run us just about $30 USD.
