The question of when or whether it's appropriate to hold a child back in school is a heated one among teachers, parents and even politicians.

And a new study is adding some kindling to the debate.

Researchers found that the rate at which kids are held back — in education circles it's called "grade retention" — has dropped dramatically. From 1995 to 2005, the overall retention rate hovered near 3 percent. But, from 2005 to 2010 it fell to 1.5 percent.

"It has pretty much gone under the radar because no one was able to measure [grade retention]," says the University of Minnesota's Rob Warren, lead researcher on the study. "The next step is why."

That's the bad news. As remarkable as these numbers are, they're also a bit of a mystery.

Working At The Why

Unraveling that mystery requires grappling with another fraught topic: social promotion. That's when a student is allowed to move on to the next grade level, staying with his age-appropriate social group, without meeting the necessary academic requirements.

Ending social promotion has long been a hallmark of the so-called accountability movement, beginning in the 1990s. The philosophy held, among other things, that schools should not promote kids who can't read or do math at grade level. Many districts tied automatic triggers to state tests, holding students back if they didn't pass.

But Warren doesn't think the drop he found has anything to do with the accountability movement or the landmark No Child Left Behind Act of 2001. "I would think No Child Left Behind would lead to higher retention rates," he says. "They're saying, 'We want to avoid social promotion. We don't want kids to move on who can't read at grade level.' "

Instead, the data show fewer students were held back, not more.

Warren considered the recession as a possible cause but dismissed it. Julian Heilig, another education researcher, disagrees. He thinks the recession — in combination with NCLB — could have led to the dramatic drop.

With the rise of a "social promotion crusade," including those automatic triggers for grade retention, Heilig says, "lots and lots of kids," particularly black and Latino students, were being held back in the 1990s.

But that created two big problems for school districts, says Heilig. First, holding kids back was costing them a lot of money. "You get this large buildup of kids repeating," he says. "That requires more space, more teachers, etc." Combine that with the fact that the recession squeezed school budgets, and holding kids back became painfully expensive.

The other problem was a bit more complicated. NCLB created incentives for schools and districts to improve their graduation rates. But most experts agree that students who are held back are then less likely to graduate. As a result, districts in Houston, Chicago, New York and elsewhere began to ease their policies against social promotion.

There's one more explanation for this big drop in the number of students being held back, and it has nothing to do with social promotion.

Kids who need help are being identified earlier, argues Britton Schnurr, a school psychologist in upstate New York who has written on grade retention. She points to a Response to Intervention model, which has grown in popularity in the past decade.

"What we're able to do is grab kids sooner, identify their needs and provide services before gaps in learning get too big to overcome," she says.

But all of these explanations are speculative. It's a question researchers now have to answer: Have school districts found new ways to help struggling kids or just new ways of hiding the fact that they're not?

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