Hundreds of teachers spent their workday Tuesday shoveling sand on Coney Island, canvassing apartment buildings with disaster relief information and assisting residents cleaning up homes badly damaged by Sandy.

With approval from their principals, the teachers opted to spend their scheduled professional development day volunteering instead.

Members of the United Federation of Teachers volunteer at the Tottenville High School evacuation center on Nov. 1.

“You feel this helplessness,” said Mark Horowitz, an astronomy teacher at Edward R. Murrow High School in Midwood, Brooklyn. “On the news, you’re watching all this, and you just want to be able to help a little bit.”

Horowitz was one of about 80 teachers from Murrow who spent the day offering assistance. He helped rip up floor boards and take down ruined dry wall in a Staten Island home.

“Everything had to come out. Everything that got wet is going to grow mold,” he said.

Horowitz said driving through Staten Island “was surreal,” and seeing curbs full of trash and ruined belongings made him feel more connected to the devastation.

“There’s a temporary dump on Midland Beach,” he said. “There’s just dumpsters full of stuff being staged on Midland Beach. It’s a park — but not right now it isn’t.”

Another Murrow teacher, Lisa Willner, spent her day with a group of teachers knocking on doors on Coney Island. She said they gave residents information about emergency assistance and school relocations.

“We just also touched base and checked in with them to see who needed what. There were some people who were still in their apartments and they have home attendants or medical needs, so we wrote down their information so we could follow up with them and make sure they got what they needed,” she said.

Willner, an English teacher, said she knocked on the door of one of her students who told her he was fine, but cold. The apartment buildings that she visited had power but no heat.

The teachers’ union helped organize the effort to get teachers out to Staten Island, Coney Island and the Rockaways. “Whole schools were volunteering,” said Michael Mulgrew, the president of the United Federation of Teachers.

Some teachers walked up and down the steps of public housing, where there was still no power, to check on residents.

“We found a couple of people today who hadn’t eaten in a week,” he said. “There were people whose medication has run out and they can’t get new medication. People have missed their chemotherapy appointments.”