At a meeting early last week, the all-Island school committee agreed to move forward in pursuit of special legislation that would allow Island towns to form a trust agreement to cover post-retirement benefits for the school district.

“It makes more sense to do it together than to do it individually,” said Vineyard schools superintendent Dr. James H. Weiss this week. The money reserved for the benefits is generally set aside in an account by each town and invested.

Committee members had questions about the process.

Priscilla Sylvia asked how each town would protect its individual contributions to a joint trust. “Are they co-mingled?” she asked. School business administrator Amy Tierney said the funds contributed will be segregated by town, so when the time comes to take money out, a specific town cannot take more than its share.

A committee will be formed to decide how funds are invested. Dr. Weiss called this the most important part of the process. “If they don’t do their job when we go to pay our bills . . . [the money] won’t be there,” he said.

Committee chairman Dan Cabot wondered how the trust would handle differences in the number of retirees in each town or district. He said that while each town and the high school should know how many retirees they must cover, there’s no way to predict how long those retirees will need the benefits. “What you don’t know is how long they are going to live,” he said.

But Katherine Logue said the system that keeps track of the retirees will update regularly. “It’s a constantly updating actuarial projection, which is the best you can do in these circumstances,” she said.

The trust would include the six Island towns plus Gosnold. Mr. Weiss said he hoped to have special legislation approved by this coming spring.

In other business, the committee approved a first reading of a new body mass index screening policy for students. Island school nurses attended the meeting to explain the screening process to the committee.

By June of 2011, the state requires that all Massachusetts schools adopt annual body mass index screening policies for students in grades one, four, seven and 10. The information can be used to calculate health risks to students.

“We know that obesity is a growing problem in America,” said Edgartown School nurse Donna Joyce. “One in four children in Massachusetts [is] either overweight or obese.” She said the screenings will complement other measures the schools have taken to help address the problem, including providing healthier food choices and offering classes in nutrition.

Results of the screenings will be confidential and will be sent home to parent. The screening is optional.