DUSTIN LUCA/Staff Photo. Teachers left Andover High School Tuesday promptly at 2:35 p.m., which is when the most recent version of their teacher's contract says they must work until. Starting Jan. 3, teachers are engaged in Work-to-Rule work action, meaning any volunteer efforts beyond the terms of their most recent contract, which was signed in 2008 and expired on Aug. 31, 2010, are likely to end as contract negotiations continue. 1/3/12

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