During Tuesday’s Democratic debate in Las Vegas, sponsored by MSNBC, the three front-runners were asked a very serious question about education.

To what do you attribute the high dropout rate among African-American students, and what would you do about it?

The question went to Illinois Sen. Barack Obama first, but eventually, Sen. Hillary Rodham Clinton and former North Carolina Sen. John Edwards answered it, too. Their proposed solutions were similar, and complementary: universal prekindergarten, after-school programs, “second-chance” schools for dropouts, promoting fatherhood, etc.

But did you notice something in common about their answers? In response to a question about kids who drop out of school, the candidates barely mentioned any thoughts they have on helping kids while they are actually in a school, during the traditional school day. After all, students are most at risk of dropping out during their freshman year of high school.

To be sure, the Democratic solutions can all be considered very important. In fact, I’ve blogged before about how fixing America’s education crisis won’t be accomplished just by fixing what goes on inside a school building.

But did Sen. Clinton forget that she’s the only candidate who actually has a dropout plan that she maintains will cut the number of kids who leave school in half? She didn’t even mention it.

Sen. Obama did mention paying teachers better and reforming No Child Left Behind (with little explanation), but he hung his answer on pre-k.

There’s little doubt that high-quality prekindergarten is beneficial for students, particulary those at risk of failure in school. But there’s also little doubt that prekindergarten programs need to be high quality. How would the next president ensure that funds are used on high-quality preschool programs, particularly for students who need help the most?

In addition, for the candidates who say pre-k will solve the dropout problem, I wonder how that helps the students who are in school now. Even if prekindergarten for every child was available this year, that does little to help the kindergarteners, and older students, who are in the system now, moving from grade to grade. Along the way, 1 million drop out each year. That’s at least 12 million kids—the population of Ohio—dropping out over the next dozen years while the candidates pin their hopes on prekindergarten.

In the debate, when asked about the economic and mortgage crisis, Sen. Clinton said: “We need to move urgently. We have a lot of big agenda items ... universal health care, college affordability -- but we can’t wait. We’re going to lose another, you know, million Americans in home foreclosures.”

What about the million students we lose every year from high schools? Does that require us to move urgently?