Brookline school officials have warned that if voters reject a proposed property-tax override, the district could face significant cuts, including more than 200 layoffs over the next three years. The district needs about $18.5 million over three years to maintain current staffing and programs, potentially leading to the elimination of 210 positions and reduction in services. This comes after a series of budget cuts in the district in which officials proposed laying off more than 20 staff members and eliminating the elementary world-language program to close a $2.4 million deficit.