I have done this before with a forward thinking Principal. Double the time that students take math and the achievement gap narrows.

From an article in the New York Times:

# ‘No Child’ Law Is Not Closing a Racial Gap

'Where we see the gap narrowing, that’s because there’s been an emphasis on supplemental education, on after-school programs that encourage students to read more and do more math problems,” Dr. Hrabowski said. “Where there are programs that encourage that additional work, students of color do the work and their performance improves and the gap narrows.”'But then there is the problem that most math teachers are familiar with:

I love it when what I read confirms what I know.'But Dr. Hrabowski said said that educators and parents pushing children to higher achievement often find themselves swimming against a tide of popular culture.

“Even middle-class students are unfortunately influenced by the culture that says it’s simply not cool for students to be smart,” he said. “And that is a factor here in these math and reading scores.”'