It can be easy to forget that Shakespeare’s Juliet, one of our most well-known heroines, is just 13 years old. The play Romeo and Juliet is about love, yes, but it’s also a tragedy about the perils and the intensity of youth itself.

So too is its 1957 graffitied musical update, West Side Story, which opens tonight and runs all weekend at the regional high school Performing Arts Center.

“The students know this world because it’s the world of Romeo and Juliet, and it’s the world of teenagers,” said director Brooke Hardman Ditchfield in an interview at rehearsal this week.

Don't mess with these ladies. — Mark Alan Lovewell

In the musical, the Montagues and the Capulets are replaced with warring gangs the Sharks and the Jets, fighting for dominance on the streets of New York. The main characters, Tony and Maria, are aged up slightly; they’re in their late teens.

The high school seniors playing them are too.

“It’s exciting and also disturbing because it’s so right,” Ms. Hardman Ditchfield said. “That’s what also makes it a tragedy.”

The two leads, seniors Emily Hewson and Curtis Fisher, have known each other since kindergarten at the Tisbury school.

“We kind of lost touch over the years, but now we’re friends again,” said Emily.

Emily has always sung alto, but when she found out last spring that West Side Story had been chosen for the annual musical, she set her sights on acquiring a soprano voice to play the part of Maria or her best friend, Anita.

The summer of voice lessons and hours of training have paid off. Emily’s voice soars in the lead role.

The boys are back in town. — Mark Alan Lovewell

“It’s pretty incredible to know that you can work on something like that,” she said.

The cast of 40 has been rehearsing tirelessly since October. This week they and a crew of 10 have spent more than five hours a day in rehearsal. Sophomore Violet Cabot is calling the cues for the show, a huge undertaking for an underclassman.

The choreography ranges from balletic swoops to salsa-inspired partner sequences to Mick Jagger head bobs. Ms. Hardman Ditchfield has meticulously arranged her many moving parts into moment-to-moment tableaus, like a series of renaissance paintings against the chain link fence that lines the back of the stage.

“It’s an incredibly demanding show,” said senior Samantha Cassidy, who plays Anybodys, a member of the Jets gang. “Even if you’re not dancing in the scene, it’s emotionally demanding too.”

The show deals with themes of prejudice, racism and xenophobia. Phrases like “Go home immigrant!” and “Puerto Rico no está en América” appear in graffiti on the set.

“Those are things people are actually saying today,” Samantha said.

West Side Story opens Thursday, Feb. 15. — Mark Alan Lovewell

A live 21-piece community orchestra conducted by Abigail Chandler will accompany the show.

“Leonard Bernstein [who wrote the music for West Side Story] wrote symphonies, and this music is at that level,” Ms. Chandler said.

At a rehearsal Tuesday afternoon, music director Jan Wightman handed out West Side Story pins to each cast member. She had written a personal note on each envelope. Ms. Wightman, who has been musical director for about a dozen shows at the high school, is retiring after this year. This is her second time doing West Side Story.

“I always wanted to do it again before I retired,” she said. “It’s an iconic musical, a great challenge. We knew they had the talent, but they have exceeded our expectations.”

Shows open Thursday, Friday and Saturday nights at 7 p.m. and Sunday at 2 p.m. at the Performing Arts Center. Admission is $15 for adults, $10 for students and seniors.