Most of the dozen states that have already gotten wiggle room from the No Child Left Behind Act don’t have very good plans in place when it comes to a key piece of the U.S. Department of Education’s requirements for turning around low-performing schools: extending learning time, according to a report out by the Center for American Progress today.

The Washington-based think-tank singled out three applications—Colorado, New Mexico, and Tennessee—as exceptionally thin, when it comes to adding time to the school day or extra time for teachers to collaborate.

And seven states—Florida, Georgia, Indiana, Kentucky, Minnesota, New Jersey, and Oklahoma—were put in the category of “committed but missing details.” Just one state—Massachusetts—was singled out as a shining star when it comes to thinking through plans for adding time to the school day.

What does extended learning time have to do with waivers? Well, it’s one of the interventions that states have to put in place in their Priority Schools (those designated as being in the bottom 5 percent of performers on the brand new accountability systems created under the waivers).

And extended learning time isn’t new to the waivers. It’s a requirement for schools using the most popular of the four School Improvement Grant models (transformation). A lot of schools have struggled with it.

Under the waivers, states can tap funds from the 21st Century Community Learning Centers to pay for adding extra time to the school day, which can be a costly venture. Those funds are normally used to cover the cost of voluntary after-school or summer programs.

Eight states of the 12 that have had their waiver applications approved have decided to take the department up on its offer, but at least five of them did not explain how the flexibility would be used, CAP found.

So how much extra instructional time is enough? Adding an extra 15 minutes to the school day isn’t necessarily going to translate into big student gains, said Jennifer Davis, the co-founder and president of the National Center on Time & Learning in Boston.

Studies have shown that the schools that really “knock it out of the park” in terms of using extended learning time to boost student outcomes tend to make their school day at least eight hours long, Davis said. (Check out one study her organization did of a school in Boston here.)

CAP had some recommendations on how the department—and states—can do a better job of implementing the extended learning time provisions in the waivers. Some of the ideas:

•The department should push states to address the lack of detail on learning time in their waiver applications;

•Districts and schools should monitor the new schedule to make sure the time is being used well;

•States should create guidance that helps districts and schools think about the current time use and how they could redesign the calendar to use time more effectively;

•Districts and schools should analyze current data to determine specific needs of their students when it comes to learning time.