Those families represent 40 students who attend Janesville public schools.
More families said they’d consider leaving town if the GM plant doesn’t reopen.
The union asked its members who worked at General Motors, Lear and SSI to respond to the survey this spring.
Seventy-two families responded to the survey, which the union put on its Web site at the request of the Janesville School District.
Twenty families said they are not planning to move away.
The numbers are difficult to interpret because it’s not known how many of the families leaving town responded to the survey.
The total number of UAW families with children in the school district also isn't known.
The district serves about 10,400 students
The numbers are important for school officials, who still are not sure how many students will show up when school resumes in September or how many more might leave town later.
Forty-nine families responding to the survey said they would consider leaving town if GM and the related companies don’t reopen or recall laid-off workers.
Altogether, families who said they’d be leaving sooner or later represent 89 students, according to school district documents. Ten of those students attend religious schools; 79 attended public schools this past school year.
Thirty-seven of the 49 families, representing 69 students, said they are considering leaving the area “in the near future.”
Every school in the district has at least one student among those whose families plan to move.
The greatest concentrations are at Craig High School, 16; Parker High, 12; and Marshall Middle School, nine.
The students are so scattered that it’s unlikely the district would be able to significantly reduce staffing.
“The impact is small because it is so spread out,” Superintendent Karen Schulte said.
A bigger impact could be in dollars. The district will lose state aid and taxing authority for each student that leaves and is not replaced by a new student moving in.
School board member Bill Sodemann said 80 students represents about $750,000 in potential aid and tax revenue.
The numbers are significant, Sodemann said, but the eventual impact is hard to gauge.
Sodemann suggested some families might stay in town because job prospects elsewhere are no better than here.
The school district surveyed parents in February with similar questions. That survey showed 10 families representing 27 children planned to leave Janesville before Sept. 1.
Another 74 families representing 107 children said in February they would leave but didn't know when.
It’s unknown how many of the families in the first survey also responded to the second survey.