The homework wars have started up again.

Last month, the superintendent of the Marion County Public Schools in Florida announced a “no homework” policy for the fall, and parents around the country are cheering. “Can we get a standing ovation for this?” wrote Wendy Wisner on the Web site Babble. “I know I’m not the only parent out there who actually dreads those busywork math and reading sheets (maybe even more than my kids).”

The district joins others in Massachusetts and Vermont that have also banned homework. But before others follow suit, they should understand that not all homework is created equal. Indeed, homework tends to be an extension of school work — good schools give useful homework; bad ones, not so much.

The combination of data and common sense show the way. A 2006 meta-analysis by a Duke University researcher found that students who did homework had better academic performance (though it was not clear which was the cause and which was the effect). But he also found that excessive homework can make kids tired and fuel negative attitudes about school.

Surely, though, it matters how much time we spend learning something. As Chester Finn, former assistant secretary of education, notes, “homework doesn’t mean any one thing. Academic work done at home can be very beneficial, much like additional academic work done in school. But it can also be a near-waste of time.”

Finn compares it to “home cooking.” You can make French fries and doughnuts in your home kitchen or you can roast a chicken and steam some broccoli. The fact that it’s home-cooked doesn’t mean you won’t make the same nutritional mistakes as at a restaurant.

But frankly, the kids who are getting the nutritional kinds of homework also tend to be those who are getting the nutritional kind of work in classrooms.

They have teachers who are challenging them at the right levels, who are encouraging them to look at some concepts on their own at home and then come to class prepared to ask questions and get clarification about certain topics.

Good schools — elite private schools or public schools in wealthy suburban districts — are most likely to be giving good homework.

But this is where the complaints most often originate. Parents say that their children have too many hours and have no time for anything else. As Wisner laments, “Don’t we all wish our kids had just a little more time for creativity and fun at home? I know I do.”

A 2002 University of Michigan study found that students aged 6 to 8 spend 29 minutes doing homework per night while 15- to 17-year-old students spend 50 minutes doing homework. There are a lot of things killing our children’s chance for fun and creativity — too many extracurricular activities, too much screen time. Homework is hardly the deciding factor.

But the same parents who claim that a few days of standardized testing a year are destroying their fragile children’s emotional state and undermining their entire educations have also come to see homework as the destroyer of childhood.

It’s true that for the children of these privileged families, homework is adding the least marginal benefit. Last summer, a teacher’s notice about abandoning homework went viral.

She wrote: “Research has been unable to prove that homework improves student performance. Rather, I ask that you spend your evenings doing things that are proven to correlate with student success. Eat dinner as a family, read together, play outside and get your child to bed early.”

If kids live in homes where all this is possible, then she’s right. Homework isn’t going to make much of a difference one way or another. Heck, third grade might not, either. But for many kids this isn’t the case. They’re not eating dinner with family. No one is enforcing a bedtime or reading with them at night.

As Finn tells me, “Total learning time does matter for students, and that’s why the most effective charter schools for poor kids have longer days, weeks, years and give kids the cellphone numbers of their teachers so they can, in effect, be in touch 24/7, including when they’re doing homework.”

For these kids, with the most effective schooling models, homework can ensure that they are learning well morning, noon and night.

Naomi Schaefer Riley is a senior fellow at the Independent Women’s Forum.