Voters in the East Islip school district overwhelmingly passed a referendum Thursday that will fund a $15.4 million energy conservation project and finance two smaller safety and building upgrade projects, officials said.

The energy conservation project, listed as Proposition No. 1 on the ballot, passed with 697 “yes” votes and 320 “no” votes, school officials said Thursday night after votes were cast at the administration building at 1 Craig B. Gariepy Ave. in Islip Terrace.

It approves funding for a contract to install energy-saving thermostat controls in school buildings along with more efficient lighting and other equipment. That would include a field of solar panels at the district’s John F. Kennedy Elementary School.

Proposition 2, which passed with 764 “yes” votes and 251 “no” votes, will allow the district to spend about $300,000 from a reserve fund on new classroom door locks and other security measures.

And Proposition 3, which passed with 721 “yes” votes and 293 “no” votes, authorizes spending $116,000 from surplus funds to upgrade a playground at Timber Point Elementary School.

The referendum comes less than six weeks before May 16, when voters in school districts statewide will decide on budgets, ballot propositions and board candidates.

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It took place amid considerable controversy over both the possibility of a tax impact from the conservation project and the voting date.

East Islip school officials have said they do not expect a tax hike would result from the project, saying they believe that a combination of state financial aid and savings in energy costs will pay for it.

Those officials acknowledged, however, that a property tax hike amounting to about $50 annually on an average home could be required if energy savings fall short of expectations.

As for the voting date, district representatives said that if voters approved the proposition for the energy project, which they did, then the district would have a head start on other school systems in applying for special state aid to pay for it.

Residents active in the East Islip TaxPac organization had urged voters to vote against Proposition 1.

Those activists contended that East Islip, where school costs already run relatively high, cannot afford the risk of an extra tax increase. They also said that if the district wants approval for a proposition to borrow money, it should place that proposal on the May 16 ballot, when more voters are likely to participate.

Propositions 2 and 3 raised no debate.

East Islip enrolls about 3,770 students. The state Education Department’s latest annual Fiscal Accountability Summary for the district calculated that it spent $15,876 per pupil in general education classes during the 2014-15 school year, compared with an average $11,051 for districts of similar need and financial capacity.