LISBON — Growing classroom sizes is driving a school spending plan that would increase taxes 7.8%.

The proposed $581,233 increase in taxes would increase property taxes by $190 to $4,810 for a home assessed at $200,000 assuming municipal and county taxes and property values remained flat, said Lisbon Town Manager Diane Barnes.

Leanna Spungen, a fourth-grade teacher at Lisbon Community School, represented a group of teachers, staff and parents on Feb. 10 when she asked the school committee to consider adding an elementary level teacher. She argued the social and emotional needs of the student are changing as educators work to keep students from falling through the cracks.

“We are doing our students at LCS a disservice by allowing the class sizes to continue to grow,” she said. “We understand that the money for teachers has to come from somewhere. We understand that this change will cost money but we believe that smaller class sizes would be the best benefit for the students and the community.”

Students need to form positive relationships with teachers, “and right now we are outnumbered, 27 to 1 in some cases,” she said.

In her three years at the school, she’s had as many as 26 and as few as 22 students. The class size reduction has made all the difference in student behavior and success, she said.

Superintendent Richard Green said the school committee has been talking about class sizes and providing enough student services for a long time. Student services often are the first to be cut in any budget. The school department is working to support not only students but also staff as teachers now struggle to deal with the social and emotional issues students bring with them to the classroom. Now class sizes have grown so that grades K through 5 are at 100 students or more.

“Our enrollment has increased so we’re looking at that,” Green said. “It’s a good problem to have.”

The school’s enrollment has been between 1,270 and 1,280 for a number of years but is on the higher side now, Green said. Increased enrollment has drawn an additional $480,000 in state subsidy for the next school year.

Green said Lisbon Community School has 663 students and class sizes there range from 14 students per teacher to 26 students per teacher. Green said the second grade has 25 students per teacher and fifth grade has 26 students per teacher. The class sizes aren’t above the state recommendation of no more than 30.

The school committee is expected to vote on the school budget Monday followed by the town council on Tuesday. A public hearing is scheduled for May 5.