It's mentioned elsewhere if you search - but the easier way to learn about it is to go to
www.singaporemath.com or Amazon.com have it. There are different editions available depending on if you buy first or 2nd hand. Basically - it's math that was developed in Singapore (I think when the British occupied over there) - and it was successful - so they bought it to California/use it in California schools and it's caught on with homeschoolers. It's got colorful pages and a progressive appraoch where everything they learn bulids on what they just learnt. If anyone else has something better to add about it / I'm not accurate - please correct me. My experience is limited.