Mayor Bill de Blasio took a backseat to Ringo Starr and Yoko Ono at City Hall Thursday as both icons promoted a music-education bus tour named after John Lennon.

Starr and Ono were also joined by actor Jeff Bridges for the John Lennon Educational Bus Tour’s fifth annual “Come Together NYC” gathering to help support the city’s school system.

The Beatles-themed event featured a “Give Peace A Chance” singalong plus a “bed-in,” inspired by Lennon and Ono’s famed 1969 protest against the Vietnam War.

Starr, Ono and Bridges participated in the bed-in while calling on youngsters to get involved in music and activism.

Reflecting on the original bed-in, de Blasio said “it shocked the world” and “opened people’s minds.”

“It still is revolutionary to imagine peace in the world, but we have to be the authors of it,” he said.

The mayor arrived at the event shortly after voting in the Democratic primary — in which he declined to endorse any of the candidates running for governor, lieutenant governor or attorney general.