PHILADELPHIA — Opponents of a proposal to tax soda to raise money for the financially troubled city school system rallied at City Hall on Tuesday, saying the plan would encourage people to leave the city to buy soft drinks and force hundreds of beverage industry employees out of work.

Tractor-trailers bearing the logos of various unions and soda companies circled the historic building, honking their horns, while several hundred people — many of them union workers — held signs urging that the idea be dropped.

Mayor Michael Nutter is pushing the 2-cents-per-ounce tax on soda and other sugary beverages to help prevent cuts in the city’s cash-strapped school system.

If passed, the tax would generate $60 million for the district this year and $80 million next year, preventing drastic cuts in school programs, according to Nutter’s office.

But the opponents conducting Tuesday’s protest estimated that the tax could cost hundreds of jobs while doubling or more than doubling the cost of soda products, from 2-liter bottles to cases. A similar plan was scrapped last year.

“This is about jobs,” said Bill Hamilton, a vice president of the Teamsters union. “This isn’t about making people healthy.”