Watertown may be the only place in the world with musical traffic lights. When the red and yellow lights signal "walk," a bell begins to ring, and blind people cross the street like everyone else.

The blind people are students and teachers at the Perkins School for the Blind, a private school with classes from kindergarten through senior high school. Perkins is Helen Keller's Alma Mater. It was the first school for the blind in the United States, and the first to educate a blind-deaf child.

Perkins, with its towers, trees and quadrangles, looks like an Ivy League college. It is quieter. There are only a few people outside; almost everyone attends classes until late afternoon. A young girl walks along a pebble path, using a cane to guide herself. A boy, perhaps eight years old, sits on a step, staring at the sky.

Inside one of the red-brick buildings, a classroom door is marked "typing class." Underneath the sign, on a piece of heavy yellow-white paper, some raised dots spell "typing class" in Braille. A blind student writes on a Perkins Brailler, a six-key typewriter designed at the school 15 years ago. She types each Braille character by pressing a combination of keys at the same time, Key number one, for example, is the letter "a." Keys one and two together are the letter "b."

She reads Braille by running her fingertips across the raised dots on the page, just as she sees flower buds in the spring by squeezing them in her hand.

In another room, darkened by afternoon shadows, a teenage boy plays the piano. He forgets a note, and has to fight back tears as he explores the cumbersome Braille sheet music with his fingers.

Elsewhere, the students swim, or study algebra, or high jump. They even bowl, with the aid of ten little bulbs that warm up to indicate which pins remain standing after the first roll.

Relaxing in his office, Edward J. Waterhouse, director of the school, tells a visitor that young boys who live at Perkins do the same things as the students at any other boarding school -- including playing practical jokes. One night, a group of boys in a dormitory set up a trap for one of their mates who had gotten out of bed to use the bathroom. While he was out, the boys built a precariously high stack of soda bottles in the entrance of the room. The boy returned, his hand gliding against the wall for guidance; he crashed into the bottles and woke up everyone in the dorm.

"All of them thought it was really funny," Waterhouse recalls.