There are actually four versions of SM, three of which are available from the official US distributor, singaporemath.com:
"original" SM: this is the third edition of the actual curriculum used in Singapore in the 90s, complete with British spellings and the metric system. Available mostly from other re-sellers, and used.
SM US edition: a minor revision of the third edition that changes the spellings to US English, and includes units on standard/customary/food-pound measures.
SM Standards edition: a more substantial revision to comply with the most recent pre-Common Core California frameworks, enabling it to be adopted by California public schools (again, pre-Common Core).
SM Common Core edition: a revision which re-arranges the topics to align with Common Core, presumably also to allow for adoption by public school districts. It also only goes up through 5B, at the moment.
The other three editions include 6A/6B, a level which consists predominantly of revision/test prep for the Singapore primary school leaving exam, and some topics in pre-algebra and data analysis.
You can also include in the Singapore family HMH's Math in Focus, a grade 1-5 curriculum with a more conventional US textbook aesthetic, and the ticket price to match.
SingaporeMath.com also has an online/digital subscription version of 1A-5B supposedly coming out this year.
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Your observation that pretty much all of his social-emotional and behavioral symptoms of concern have lessened markedly since leaving his school environment definitely validates your decision to pull him out. If there are true areas of vulnerability that will need remediation or therapy in the future, they will re-emerge on their own. Don't blame yourself for the past three years. You did the best you could given the information and resources you had available to you. (And perhaps there may have been some genuine social skills deficits that needed therapy at the beginning--after all, something brought you to special ed to begin with.) Enjoy the fresh opportunities of today and tomorrow. And find something fun to do with all that gas money!
