How can students learn math, when the teacher doesn't know much more about the subject than the pupils? That's one of the questions raised by a new report by a children's advocacy group, the Education Trust.

The report is based on Education Department data. It says in high-poverty schools, two in five math classes have teachers without a college major or certification in math.

And in schools with a greater share of African-American and Latino children, nearly one in three math classes is taught by such a teacher.

Math is considered a "gateway" course, one that leads to greater success in college and the workplace. The crucial learning time for students is in grades 5 through 8.

Researchers acknowledge it can be tougher to find qualified teachers for middle schools, especially in low-income areas.