PORTLAND – Research shows that small classrooms are beneficial during a child’s earliest school years.

But there is little evidence that shows a correlation between class size and student achievement beyond the third grade, education researchers say.

The issue is coming up with Gov. John Baldacci’s sweeping reorganization plan for Maine’s school system. One of the plan’s proposals calls for less state funding for teacher salaries, resulting in higher student-teacher ratios in grades six through 12.

Nationally, a class-size reduction experiment in Tennessee in the 1980s showed that small class sizes for the early grades boosted student achievement through high school and beyond. The Student-Teacher Achievement Ratio study compared the performance of pupils in classes of 13 to 17 pupils to classes of 22 to 25 from kindergarten through third grade.

“Students who started in small classes in kindergarten and stayed in small classes through at least grade three were about a year and a half ahead of their peers [in the larger classes] by the time they graduated high school,” said Charles Achilles, a Seton Hall University professor and one of the study’s principal investigators.

Deciding where to spend limited education resources can be tricky, said Brian Stecher, a senior social scientist at the nonprofit Rand Corp. in Santa Monica, Calif.

There aren’t any studies comparing the benefits of a dollar spent on teachers to a dollar spent on computers or a dollar spent on scholarships.

Still, no parents want to see their children’s classrooms get bigger, he said.

“Parents and teachers are almost universally in support of reducing class size if possible,” he said.

In Maine, a recent analysis compares the results of Maine Educational Assessment tests in different school districts.

The results show virtually no difference in the student-teacher ratios between high- and low-performing schools, said David Silvernail, director of the University of Southern Maine’s Center for Education Policy, Applied Research and Evaluation.

“The ratios aren’t driving performance,” Silvernail said.

Maine will continue to have small classroom sizes even if the allocation funding formula is changed.

A ratio of “17-to-1 is still considered a very good class size nationally,” said Education Commissioner Susan Gendron.