Chicago teachers who walked out on students to protest for a bigger paycheck are “working like the devil,” former vice president Joe Biden told his comrades in the Windy City.

Biden phoned it in to the massive Chicago Teachers Union strike on Friday, offering support to CTU President Jesse Sharkey and about 35,000 other educators and union support workers who ditched students to picket in front of schools in the cold.

“Vice president Biden you’re here on the picket line with the CTU,” Sharkey shouted into his cell phone amid a mob of red-shirted educators in a video posted to Twitter. “Do you have any message for them and I’ll try to relay it best I can?”

The video cut to Biden relaxing indoors on a leather sofa chair, from where he offered a series of union talking points and gushing praise for the folks freezing on the front lines. Weather data shows it was just over 40 degrees when CTU members hit the picket lines Friday morning, though it warmed to the mid-50s by Biden’s mid-day call.

“Well, I tell you what,” Biden said, looking down to his notes. “Tell everybody I admire what you’re doing. You know, what people don’t get is, you know, teaching is not what you do, it’s who you are.

“And it’s all about the kids. And you guys are out there working like the devil!”

Sharkey relayed the remarks, but omitted the satanic reference.

“He says he admires what we do,” Sharkey said, repeating what everyone in the proximity could already hear through his phone speaker. “It’s not just what we do, it’s who we are. And we’re out here working as hard as we can.”

The video cut back to Biden preaching from his wood-lined cocoon of comfort.

“What people don’t realize unless they focus on it is you’re working for the children,” Biden said, raising his voice. “It’s not about you, it’s about the children.”

Sharkey echoed: “It’s not about us, it’s about the children and he admires what we’re doing.”

A few nearby cheered.

“Ok, I’m going to give that message and um, uh, I’m sure you’re busy, I’m going to let you go but I really appreciate your call,” Sharkey shouted to Biden over police sirens blaring in the background.

Biden heaped it on before signing off.

“No, no – I appreciate what you’re doing. I mean this sincerely. I’m really proud of you, man,” the 76-year-old said. “Really proud of you.”

“Thank you very much, vice president,” Sharkey said.

The coordinated call comes as Biden struggles to maintain frontrunner status in the Democratic presidential primary to take on Trump in 2020. The former vice president faces fundraising challenges tied to numerous speaking gaffes and shifting policy positions, which recently prompted Biden’s campaign to renege on a promise not to accept money from political PACs tied to corporations and special interests.

The CTU, meanwhile, is holding hostage the education of more than 360,000 students over raises for union members and staffing numbers in schools, which directly corresponds to the number of union members paying $1,000 in annual dues.

Chicago Public Schools officials canceled classes for the eighth day on Monday as contract negotiations continued without much progress.

CTU Vice President Stacy Davis Gates told WGN the union and city are $38 million apart, while CPS COO Arnie Rivera contends the CTU is demanding $100 million more than the district can afford.