TORONTO — From Windsor, Ontario, it’s just a 10-minute drive over the Ambassador Bridge or through the Detroit-Windsor Tunnel to downtown Detroit. People cross all the time to work, shop, visit a gallery, go to a show or a game. Taxis regularly make the trip, and there’s even a Windsor city bus route through the tunnel.

But President Trump’s policies about who will be allowed to cross the border have Canadians so worried that school officials in and around Windsor have decided to suspend all student field trips to the American side.

“It was the prudent thing to do because there is so much confusion and uncertainty,” said Scott Scantlebury, spokesman for the Greater Essex County District School Board, which represents 35,000 students, many of them immigrants or the children of immigrants. “We don’t want to have some student turned back at the border, or even held up for a period of time.”

The school board’s decision was just one sign of the growing apprehension on the Canadian side of the border.