It's being standardized now across most states. It looks like quadratic equations are in high school.
http://www.corestandards.org/Math/Content/HSA/APR
"The Standards set grade-specific standards but do not define the intervention methods or materials necessary to support students who are well below or well above grade-level expectations."
I.e., this defines what constitutes "grade-level" skill sets, but lots of better schools will exceed those standards by one or more years - their 10th graders may be operating at the 12th-grade standard, etc.