CHICAGO — Chicago opened public school classrooms this week for the first time since the spring, but 18 percent of teachers and staffers required to return Monday did not do so, according to the school district, which is starting disciplinary procedures against some employees.

On Monday night, Chicago Public Schools notified 145 employees that they were considered absent without leave and that their pay would be docked beginning Tuesday. Some teachers who spent Monday teaching virtually instead of returning for in-person instruction were also locked out of their Google Classroom accounts in the evening, according to a district email that many teachers received.

“The vast majority of educators who are needed back in schools have returned to work and we are making sure the relatively small number of staff who have chosen not to support our returning students are held accountable,” district spokesman James Gherardi said in a statement.

Thad Goodchild, a lawyer for the Chicago Teachers Union, said the district is in violation of its contract — something city officials debate — and state law for withholding pay from educators who are working remotely and providing remote instruction during the pandemic.

Goodchild said the union will file a class-action grievance, under its labor contract with the district, “on behalf of any members whose pay Chicago Public Schools docks while working remotely, as it has heartlessly threatened to do.” He said the district faces wage-theft liability under state law.

Chicago preschool teacher Kirstin Roberts, 52, was one of the district teachers considered absent without leave. She spent Monday teaching her 22 students virtually from home.

Shortly after finishing her teaching day, Roberts received an email notifying her she was considered absent without leave until she reports on site for work. Two hours later she was locked out of her Google Classroom account and other district tools that would allow her to teach virtually.

Roberts called the situation “upsetting,” since she would like to continue teaching her students online — all of whom, she said, have opted to stay home instead of returning for in-person instruction.

“I live with my mom, who is elderly,” said Roberts, who teaches at the Brentano Math and Science Academy, an elementary school. “She has very serious health conditions. She has a brain condition. She has no bladder, and she had lung cancer this past year. I cannot bring this home to her.”

The district said it began initiating the AWOL process on 145 of approximately 210 employees who were issued final notices if they did not appear in person Monday.

“I’m not AWOL,” Roberts said. “I’ve been teaching every day. My principal knows it, and all of my parents know it.”

Officially, it is the district’s policy that an employee must be absent for 10 consecutive days to be considered AWOL.

Chicago Teachers Union President Jesse Sharkey accused the district of bullying and threatening staffers by demanding they return to work. Citing the need for better procedures, Sharkey said there is not clear direction on what educators should do if there is an outbreak in a school, or what conditions would prompt closures if there is a coronavirus infection or outbreak.

“We don’t feel like we’re being listened to,” Sharkey said. “We’re raising reasonable concerns.”

Linda Perales, a special-education teacher at Corkery Elementary who did not return to work, also had her Google Classroom account suspended and said she is no longer being paid. “I don’t think it’s safe, because we know that our cluster students cannot wear their masks all day,” she said Tuesday morning at a news conference hosted by the union. “We have been told that we need to build their tolerance to wearing their masks all day, which implies they cannot wear their masks all day. This is an airborne virus, and not wearing a mask puts everyone at risk.”

The district said more than 6,000 pre-K learners and diverse learners of all ages who needed “moderate to intensive support” had opted in under the city’s tiered plan. It did not provide the number of students who ultimately returned for in person learning Monday.

Mayor Lori Lightfoot (D) said that while remote learning works fine for some students, “it doesn’t serve all students equally or well.” She contends reopening schools is part of a bigger plan to get Chicagoans back to work.

“We can’t get any of the other things done that are necessary — whether it’s economic development, whether it’s addressing the violence in our neighborhoods, the mental health and the trauma — if we don’t have a strong and vibrant, healthy public school system,” Lightfoot said. “It is core. It is the ecosystem. It is the skeleton on which we build everything else.”

Parents Sue Wojcik said her 4-year-old daughter was excited to go to preschool in person and could not stop talking about it. When she got home Monday she wanted to go to bed early so she could go to school again. The hardest part, Wojcik said, was coaching her daughter not to hug friends or teachers.

“She was excited to finally meet all of her friends she saw on Google during remote learning,” Wojcik said. “I was happy that she was happy. Going back was the right thing for her, because she’s super social.”

Wojcik, a part-time veterinarian tech at an animal hospital who is married to a Chicago police officer, said that although she does not want anyone to get sick, having her daughter attending in-person class has helped her and her husband, who have continued to work and frequently interact with the public during the pandemic. “You’ve got to work,” she said. “The school is doing what they can, and remote learning isn’t working for everybody.”

Catherine Henchek, whose son has epilepsy and cognitive impairments and is part of the all-ages diverse-learners group invited back for in-person learning, opted out of sending her son back to school.

Henchek said she had to have a “hard conversation” with her son after he saw some of his classmates learning in person at school, some without masks, while he attended class remotely.

“At first he wanted to go, because he wanted to play sports,” Henchek said of her son, who usually arrives at school at 6:45 a.m. so he can get extra time to play basketball before school. After explaining that sports are not taking place and how she was concerned that the virus was still spreading, Henchek said, she had to reassure her son that all of his friends were not going to die because they went to school.

“It was very difficult, but I don’t think going back in person is safe at all,” Henchek said.