THREE LAKES, Wis. (AP) — A small school district in northern Wisconsin has adopted a new policy about political activity after some staff members unknowingly showed up in a campaign ad for Republican Gov. Scott Walker.

It wasn’t immediately clear when the footage was taken, but the ad shows staff from the Three Lakes School District expressing their gratitude to the governor for education funding.

“I found it to be alarming because it clearly did put the school in a position of publicly supporting a candidate,” said Tom Rulseh, the local school board’s president. “At best, I suspect that the advertisement came about as a result of a combination of naivety and poor judgment.”

The ad was funded by the governor’s campaign. The school board said it was told the ad would stop running on TV and online.

The school district voted on the policy at a special meeting Thursday. The policy bars employees and the board from engaging in political activity or showing any political preference during work hours.

Three Lakes Superintendent George Karlin apologized for the ad and accepted responsibility for the situation.

“Recently I failed to vet the purpose of the governor’s visit as thoroughly as I should have. This was a mistake on my part, and I apologize for that,” Karling said.

Rulseh said the board was aware of the governor’s visit but didn’t know it would lead to a campaign ad.

Some people in attendance at the meeting said the policy reiterates something that was already expected of public employees.

“Every teacher knows that in a classroom, they cannot give any of their political persuasion to their students,” said resident Lynn Zibell.