Homeschoolers are exempt from these "assessments" under the No Child Left Behind Act thanks to HSLDA.org HSLDA (Home School Legal Defense Association) does a fantastic job of staying on top of legislation issues. They really came through for us in Minnesota last year when a Senate bill threatened to tighten regulations on homeschoolers. (we were part of the crowd at the State Capitol!)
Minnesota home schoolers defeat attempts at more regulation http://www.hslda.org/docs/news/hslda/200103220.asp
The exemption from the assessments varies from state to state. Home-schoolers in Massachusetts turned out in record numbers several years ago to protest pending legislation that would have required their participation in MCAS. They won a "stay". They could "choose" to have their students take them or not. That was well before the assessments and many of the standards were in final draft form. The assessments at that time had not reached the "high stakes" level that they are nearing now. I would urge you remain vigilant. Some states are nearing the point where you will need that Assessment Seal on your record if you want to go on to any level of higher education. Then what?