From Watertown Square/Center, pick up Galen Street heading toward the Mass. Turnpike. At the end of Galen Street, turn right onto Washington Street. Once on Washington Street, move to the left of the street as you will go over the ramp spanning the Turnpike (it goes around the Sheraton Tara Hotel). Once you go around the hotel, move over to the right of the roadway to take the very next right turn onto Centre Street (there's a pharmacy on the corner as you turn.)
Go to the first set of lights and turn left onto Church Street (the Eliot Congregational Church will be on your left at this corner. Proceed on Church Street, through a stop sign at the first block. As you proceed up Church Street, you'll come to the top of the hill. At this junction, turn left onto Park Street (which is one way). Proceed down Park Street and you'll come to the school's parking lot.