Kansas City, Mo. ? Forget about students spending one year in each grade, with the entire class learning the same skills at the same time. Districts from Alaska to Maine are taking a different route.

Instead of simply moving kids from one grade to the next as they get older, schools are grouping students by ability. Once they master a subject, they move up a level. This practice has been around for decades, but was generally used on a smaller scale, in individual grades, subjects or schools.

Now, in the latest effort to transform the bedraggled Kansas City, Mo., schools, the district is about to become what reform experts say is the largest one to try the approach. Starting this fall officials will begin switching 17,000 students to the new system to turnaround trailing schools and increase abysmal tests scores.

“The current system of public education in this country is not working” said Superintendent John Covington. “It’s an outdated, industrial, agrarian kind of model that lends itself to still allowing students to progress through school based on the amount of time they sit in a chair rather than whether or not they have truly mastered the competencies and skills.”

Here’s how the reform works:

Students — often of varying ages — work at their own pace, meeting with teachers to decide what part of the curriculum to tackle. Teachers still instruct students as a group if it’s needed, but often students are working individually or in small groups on projects that are tailored to their skill level.

For instance, in a classroom learning about currency, one group could draw pictures of pennies and nickels. A student who has mastered that skill might use pretend money to practice making change.

Students who progress quickly can finish high school material early and move forward with college coursework. Alternatively, in some districts, high-schoolers who need extra time can stick around for another year.

Advocates say the approach cuts down on discipline problems because advanced students aren’t bored and struggling students aren’t frustrated.

But backers acknowledge implementation is tricky, and the change is so drastic it can take time to explain to parents, teachers and students. If the community isn’t sold on the effort, it will bomb, said Richard DeLorenzo, co-founder of the Re-Inventing Schools Coalition, which coaches schools on implementing the reform.

Kansas City officials hope the new system will help the district that’s been beset with failure. A $2 billion desegregation case failed to boost test scores or stem the exodus of students to the suburbs and private and charter schools. The district has lost half its students and will close about 40 percent of its schools by the fall to avoid bankruptcy.

Covington wants to start the system in five elementary schools in hopes of spreading it through the upper grades once the bugs are worked out.

“This system precludes us from labeling children failures,” Covington said. “It’s not that you’ve failed, it’s just that at this point you haven’t mastered the competencies yet and when you do, you will move to the next level.”