My son is 11 and is autistic. I pulled him out from public school this year. I don't know his actual grade level so for Math I signed up for www.ixl.com and started him from K and see where he's lacking. This will be a very good start for your 6 years old. It builds skills and everytime you make a mistake, it will keep on giving you more problems till you master the skill.
If he's advance, you can move up anytime. You can view or print out his performance. You can also supplement it with workbooks if you want. But for me, this is a stand alone skill builder.
My son just turned 7, and we are eclectic .. I make my own curriculum, which is mostly unit studies, with breaks that incorporate learning in fun ways in between (like math secret code treasure hunts, writing letters/stories, science experiments, math tag, playing store, converting board games into math, etc.) :-) It has worked pretty well for us so far, and will be doing the same this year. :-)
Like SarahNElijah, I am eclectic, and create much of my own curriculum. When I do use curriculum, I find that I like what other home educators have created, because they created their curriculum to fill a need that standard curriculum was not fulfilling...."Home School is not the classroom".
We just finished her first grade year using a Catholic based phonics program called Little Angel Readers. We used a Science book from Catholic Heritage Curricula, the book is called Behold and See 1. And we started Math U See Alpha in February so we are continuing it through the summer. We use Rosetta Stone for spanish. That's about it for now. I'm going to buy the full Curriculum from Catholic Heritage Curricula for second grade in a month or so, except Math we will continue Math U See. But for now we are enjoying learning through play focusing on my 4 year olds level but involving all the 6 year old and 10 month old.
Hooked on Phonics (the end of grade 1 and probably all of grade 2) Math U See Alpha Life of Fred: Butterflies and Cats Story of the World: Book2 along with his 8yo brother. Plus some geography that I do myself Jan Van Cleave's Chemistry for Everykid; The Way We Work; The Night Sky book; Roots, Shoots, Buckets and Boots; Mary Jane's Outpost; and the Encyclopedia of Country Living (all for science) Can You Find It? (by the Metropolitan Museum of Art)