Good news for younger children on the Nation's Report card. 9 year olds appear to making significant gains in reading and mathematics, but the gains certainly flatten out by age 17.
For mathematics, a favorable trend was also seen at age 13, but the 17 year olds' dip occurred again.
High school dropout rates may also be as high as 30-40%, though, and this number may climb if students can't meet state requirements.
NAEP - The Nation's Report Card
NAEP Press release
Fudging High School Graduation Statistics