Following controversy this spring around a parent proposal to raise funds to expand the auditorium at the Heath School, the School Committee has voted for a policy that clarifies its policy on donations. The new policy, which is the first of two revisions that would apply to future large capital campaigns, stresses that the town’s schools are primarily a public responsibility, to be funded by taxes. Private donations are allowed if they are unrestricted, or are consistent with the district’s priorities, supplement public funds, and won’t create a need for future public funds for items like maintenance. The new policy, which was approved at the School Committee’s Sept. 27 meeting, “wouldn’t preclude” a private fund-raising campaign for a school expansion, said Rebecca Stone, chairwoman of the board’s policy subcommittee. Under the new policy, a project in the district’s capital improvement program that is planned but not fully funded can be aided by private donations, she said.