LEWISTON — Most Lewiston schools still have space for prekindergarten students, Superintendent Bill Webster said.

The exception is Farwell Elementary School, which is full, and Martel, which sends its pre-K students to McMahon Elementary School.

Parents interested in enrolling their 4-year-old children should contact their school. Webster doesn’t expect the space to go unfilled.

Pre-K classes begin Sept. 6, the day after Labor Day.

School opens for most students in kindergarten through grade nine Aug. 31. School begins Sept. 1 for grades 10-12.

Webster said that last year at this time Lewiston had pre-K openings, but by the time school started in September, the schools were completely full with a waiting list.

“This year, there are more open slots,” he said. “We do have to do more education — reaching out to parents, make them aware of the openings and advantages of children being enrolled in pre-K.”

Meanwhile, Auburn’s pre-K classrooms are already full, said Superintendent Katy Grondin.

Public schools are encouraged by the Maine Department of Education to offer pre-K, but it’s not mandated. The state reimburses public schools for pre-K students. Unlike other grades, public schools do not have to accept more students once classes are full.

There are two reasons why there’s some room this year, Webster said. Lewiston has added another pre-K classroom, which means Lewiston will have about 300 pre-K students.

Also, about 70 Lewiston students are attending Lewiston’s new public charter school, Acadia, which is opening this fall, Webster said.

About 65 percent of incoming kindergarten students have attended public or private prekindergarten classes.

“Given the nature of our population, I’d love to see that percentage be 75 or 85 percent,” Webster said.

Students who especially benefit from pre-K are those who do not have enriching activities to learn school readiness, are not read to or exposed to books, or those who are not in playgroups where they learn how to interact with other children.

Most of Lewiston’s pre-K programs are half-days, with one class in the morning and another in the afternoon. The exceptions are Montello and Longley, which have five-hour programs.

A child needs to be 4 years old by Oct. 15 to enroll.

Families do not pay for public pre-K programs; it is free. Transportation is provided, Webster said.