HIGHLAND PARK, Ill. (CBS) – Parents in the North Shore School District are bracing for a possible teachers’ strike beginning Tuesday.

Teachers picketed Monday afternoon in a show of solidarity as last-ditch negotiations continued between union representatives and District 112′s school board.

It looked like business as usual at local schools, with parent picking up their children from school. But Tuesday, things could be different.

Parents won’t know for sure until they receive an email expected at 5 a.m. Tuesday. The district planned to open three school buildings as “activities centers” for children.

Laurie Wurster says the wait is “very stressful.”

“Just not knowing how long it’ll last is what I’m worried about,” the parent told CBS 2′s Dorothy Tucker.

Everyone is in limbo because teachers and the school board haven’t been able to reach an agreement on wages, insurance and retirement benefits.

Those are the same issues that led to strikes in four other districts in the last month. Also similar: teachers walking off the job after classes have started.

Pamela Kramer, president of the North Shore Education Association, says there’s no connection.

“I think that’s more of an indication of what school districts are trying to do to teachers,” she said Monday.

Kramer says teachers are asking for a 3.25 percent raise, while district officials say they’re offering a 1.5 percent increase. Both sides have been trying to come to an agreement since the spring.

Bruce Hyman, president of the District 112 school board, says the labor unrest among teachers in the Chicago region indicates “the economy is still a significant issue.”

There are 4,500 students in the district, which serves Highland Park, Highwood, and Fort Sheridan in pre-kindergarten through 8th grades.