When I bought Singapore Earlybird, they only offered the Standard edition. It seems to offer more and people seem to like the format/HIG better. "Standards is the newer one with the few additional topics and topics rearranged to fall more in line with California state standards."
I looked at my copies and my Standard edition does use US currency. So I don't think it means metric verses feet/inches stuff, although I could be wrong. Is the main difference that the Standard edition follows CA's state standards then?
Here's a comparison of the two:http://www.singaporemath.com/v/vspfi...andSTD2008.pdf