A program called Success for All, born in Baltimore 26 years ago to improve elementary schools, has set a record for most glowing reports from tough researchers.

But the latest study showing how well it works also hints at why it has not become more popular: It uses ability grouping and scripted lessons, both disliked by many teachers.

Success for All is found in four schools in Alexandria and three in Prince George’s County. Those numbers might increase in light of a new report by the well-respected research group MDRC. The report says that Success for All kindergartners did significantly better than similar students in 18 control group schools based on a standardized test of phonics.

That endorsement by researchers can be added to past accolades. A comparison of whole-school reform models by the Washington-based American Institutes for Research in 1999 gave Success for All and Oregon-based Direct Instruction the highest ratings. And a three-year study by the Philadelphia-based Consortium for Policy Research in Education in 2009 revealed that Success for All moved students from the 40th to the 50th percentile in reading between kindergarten and the end of second grade.

The school improvement model, the brainchild of Johns Hopkins University researchers Robert E. Slavin and Nancy Madden, has spread through much of the country, with 500,000 students in 1,000 schools. It received a $49.3 million grant in 2009 from the federal i3 program to add more schools and increase training for teachers and staff members.

But it still gets a grumpy response from many policymakers. During the Bush administration, despite a rash of new education spending, Success for All got little notice. From its beginning, when a Maryland political dynamo named Buzzy Hettleman challenged Slavin and Madden to create a practical program for Baltimore schools, teachers have complained about being told what to say in class and how much time to devote to each lesson.

The MDRC study gathered not only test data but attitudes of teachers in the Success for All and control group schools. In the Success for All schools, 54.8 percent agreed or strongly agreed that their reading program was too rigid or scripted. Only 19.8 percent of the control group teachers said that about their non-Success for All programs.

Ability grouping — dividing students into groups based on their achievement levels — has also been standard for Success for All, with a twist. In traditional ability grouping, students rarely move from a lower to a higher group. Success for All dictates that every child be reevaluated every two months with an eye to moving those who are doing better up to a higher group.

The MDRC study found that 96.9 percent of Success for All teachers said their students were grouped by ability for reading, compared with only 54.8 percent of teachers in the control group.

It is startling to see Slavin and Madden, a couple of progressive sensibilities who met as undergraduates at left-leaning Reed College, criticized for methods seen by many educators as too conservative and restrictive. But they have gone with what works for kids and have an unusual rule that limits faculty resistance to their ideas. They won’t let a school have the program unless 75 percent of the teachers have voted for it in a secret ballot.

According to MDRC, which plans two more reports on the program, Success for All beat the control group by about 12 percent of the average annual growth for kindergartners.

Programs as old as this one are often rejected as out-of-date by school districts. But can this region’s school leaders, who often say they base their decisions on research, afford to ignore something this successful?