As principals’ tenure decisions come under harsher scrutiny than in the past, one principal has found a new way of proving that his teachers deserve the honor.

Last year, when Fortunato Rubino, the principal of a high-performing Williamsburg middle school, wanted to grant tenure to one of his teachers, his superintendent wouldn’t sign off because the teacher had a low effectiveness rating. Scenarios like this are becoming more common as the DOE tries to make tenure tougher to earn and asks superintendents — who have the final word on tenure — to consider teachers’ value-added scores. These scores measure how well a teacher’s students performed on the state math and reading tests compared to how well a predictive model thought they would do.

So this year, when six of his teachers are up for tenure — including the one who didn’t get it last year — Rubino plans to introduce his own evidence.

During a visit to his school I.S. 318 this morning, I watched Rubino pull three DVDs out of his briefcase — each carefully marked with a teacher’s name. For all six teachers who are up for tenure, Rubino has filmed a lesson and burned the videos to DVD for his superintendent to watch. He told me he’d spent the weekend going through the videos to make sure each showcased his teachers at their best.

“Who’s going to argue with that?” he said. “If you’re going to say to me, ‘Well I don’t want to tenure that teacher,’ then you’re going to have to look at that lesson and say this person can’t teach.”

The number of teachers who were denied tenure increased last year, but it remains small. In 2009, 2.3 percent of teachers who were up for tenure were denied it. In 2010, that percentage rose to 3.7. More teachers are also having their probations extended. From 2009 to 2010, that percentage rose from 4.5 to 7.2.