The League of Women Voters of Newton has decided to back Mayor Setti Warren’s proposal for a $11.4 million override of Proposition 2½. According to the league’s website, members voted overwhelmingly on Jan. 10 to support the override package, which includes three separate ballot initiatives to fund new schools, road repairs, fire station buildings, and day-to-day operations of the city. The league’s support gives Warren a boost as he tries to persuade voters to pass the first property tax override in a decade. The citywide vote is scheduled for March 12. If voters approve all three increases, officials estimate that the annual taxes on a $686,000 house — the median-priced home in the city — would go up to $8,006, an increase of $343.