I'm trying to give the OP the benefit of the doubt here, and assume that she's misunderstood what SATS are and got herself into a panic.
OP, what do you think SATS are for?
My understanding is this: SATS are not like GCSEs or A-levels. They and the ongoing assessment that teachers undertake throughout the year (every year) are not there to test children as such - they are there to make sure that the school are doing their job and to identify room for improvement (both for pupils and teachers).
If you feel your dd's school isn't stretching her, then you need to address this with them. However I also get the feeling that you need to get a grip relax a little.
If, after approaching them rationally and listening to them you feel the school can't give your dd what she needs, then look for another one.
For goodness sake though don't keep her off school - not yet - that's madness!
In the meantime, support the school and the work they're doing with her - remembering that your dd is 6. She might be a genius, but forget trying to push, push, push her - instead spend time with her fostering and developing interests in ways the school are less equipped to do.
Help her (subtley, please) to understand mass and volume by doing a bit of baking. I'm sure you could get some division in there easily enough. Talk about the seasons on country or city walks. Help her writing skills by encouraging her to write to her grandma. These things, the things I expect you're doing already, are far, far more beneficial than pulling her out of school and they are not "work" so no need to feel bad about making her "do stuff in the evenings".