The Kehillah Schechter Academy will hold its final graduation tomorrow and will close its doors after 25 years on Tuesday. Gregg Rubenstein, president of the school’s Board of Trustees, said the school did not have enough students for next year to continue to operate. In general, he said, rising costs and less interest by parents to send their children to religious schools contributed to the decision. “It’s a very challenging environment in which to operate,’’ he said. He said the school’s enrollment dropped from 240 a few years ago to its current 110, of which 22 are graduating. “It’s incredibly difficult. The school’s closing is a tragedy on so many different levels,’’ said Rubenstein, who has one daughter graduating and another who will be transferring to school in Sharon. He said the 40 staff members, many of whom will be looking for new jobs, have been helping students to transition to other schools. The school building, located at 1 Commerce Way, will be sold, with the money going to the mortgage holders.