SWAMPSCOTT – Selectmen voted unanimously this week to support a lawsuit challenging the fairness and constitutionality of the state’s Chapter 70 education funding legislation that they say shortchanges the town.”There’s a formula that divvies out money to each community and each community gets a certain amount of money from the formula,” explained Selectman Richard Malagrifa on Thursday. “We are really not getting our fair share, which means we’re paying more of our property taxes toward education rather than other things.”The state annually funds public schools through the Chapter 70 legislation, which uses a complicated formula based on property values, residents’ income levels and other data to allocate the state’s contribution to local public schools. The state must pay a minimum of 17.5 percent of the school budget, according to the law.But the formula has resulted in several communities getting less than the minimum, according to town officials.Resident and former School Committee Chair David Whelan said that state figures show that Swampscott, for instance, received 13.86 percent of their 2012 school budget from Chapter 70, underfunding the schools by more than $600,000, he said.But while the funding formula hurts Swampscott, other communities receive more than their targeted amount of state funding – resulting in widespread acknowledgment that the funding formula is “broken,” as Gov. Deval Patrick said last October, but making politicians reluctant to pursue reform, Whelan said.”The state has a constitutional authority to fund education – (it) has not lived up to that responsibility,” said Whelan. “All we’re trying to do is make the argument that what’s going on right now is not fair and equitable ? how the fairness comes in and we can shuffle the pieces so that we can properly educate our kids is up to the state elected officials.”Selectmen voted Tuesday to continue a process that the town – along with the towns of Hamilton, Wenham, Essex and Manchester and the nonprofit Tax Reform for Education, Inc. – began last year to see if there was a case for a lawsuit, Town Administrator Andrew Maylor said after the meeting.