Here is the short of it: Adequate Yearly Progress (AYP).
The federal No Child Left Behind Act of 2001 (NCLB) requires states to set annual measurable objectives (AMO) of proficiency in reading and mathematics, participation in testing, and graduation and attendance. Schools and school divisions that meet the annual objectives required by the federal education law are considered to have made adequate yearly progress (AYP) toward the goal of 100 percent proficiency of all students in reading and mathematics by 2014. For the 2011–12 school year, the AMO was a pass rate on the SOL tests taken in the 2010-11 of 86% for reading and 85% for math. These pass rates must be achieved by all of the following subgroups in a school: All students, white, black, Hispanic, students with disabilities, economically disadvantaged students, and students with limited-English proficiency.
If you are in Virginia, go to the link below and locate your schools name and click on it to see your schools past 3 year data for AYP and Accreditation. I hope this was helpful for you.