If Windsor follows Wiscasset’s lead and pulls out of Regional School Unit 12, the district will have to figure out where to send Somerville’s students, Superintendent Howie Tuttle said.

Both Windsor and Palermo have negotiated withdrawal deals with the district and are set to decide on them Nov. 4.

It’s the same vote Wiscasset faced in November 2013, with a yes vote triggering a departure the following July. But in Windsor’s case, departure would mean that, after year one outside the district, Somerville students could no longer attend Windsor Elementary School, Tuttle said Sept. 19.

It started looking that way to Tuttle when he poured over the state law; at a meeting in Augusta on Sept. 15, Maine Department of Education Commissioner James E. Rier Jr. confirmed it, Tuttle said.

The situation turns on the fact that, unlike fellow member towns Alna and Westport Island, Somerville didn’t come into the district with school choice for kindergarten through eighth grade. So, even if the district and Somerville parents would prefer to keep sending students to Windsor, that will only be able to continue if Windsor stays in the district, Tuttle said.

A November decision by Windsor to leave, effective July 1, 2015, would mean the approximately 45 Somerville students who attend school there would be at another school by September 2016.

If it comes to that, Tuttle said that whatever arrangements the board makes should not impact costs for member towns. Other schools in the district have room, he said. Options include placing Somerville’s students in schools in Whitefield, Chelsea, or back in Somerville. The school there has been put to other uses since local students started attending Windsor Elementary, Tuttle said.

Where would the Somerville students most likely go, if the district loses Windsor? “That’s for the board to decide down the road,” he said.

Wiscasset, Westport Island, Alna, Whitefield, Somerville, Palermo, Chelsea and Windsor opened the district in 2009, during the state’s wave of school consolidation. Wiscasset’s withdrawal took effect July 1. In June, Westport Island voters decided to stop pursuing a possible pullout.