Cash-strapped school districts around the country are looking more closely at proposals to sell advertising on the interior and exterior of school buses.

In Miami, the school board has approved a plan to sell advertising on the interior of the district’s school buses.

The approval came on a 6-3 vote, with some board members expressing concerns about possible inappropriate messages being displayed in the buses.

Although the district would be able to refuse any ads, one board member feared that a rejected advertiser would sue the district on the grounds that its First Amendment rights had been compromised.

The vote by the board at Miami-Dade Schools is not binding. It authorizes school district staff to negotiate a contract for final approval later this summer.

Farther south in Palm Beach County, Fla., the school board is reconsidering a plan to sell ad space on the interior of school buses.

It rejected the plan last summer because of concerns about exposing captive students to commercial messages, but a looming budget shortfall has prompted board members to rethink the proposal.

“This is a real golden opportunity without cost to us,” Bill Graham, the Palm Beach County School Board’s vice chairman, told the Palm Beach Post.

What the school board is considering is a plan to piggy-back an advertising program with Putnam County Schools, which signed a school bus advertising contract last year. With 150 buses, Putnam County has been unable to generate any advertising revenue. By adding Palm Beach County’s fleet of 600-plus buses to the mix, however, it might be able to sway potential advertisers.

Under the proposal, School Bus Advertising, the company that signs up the advertisers, would keep 75 percent of any revenue generated. The school district would get the rest.

School district officials in Putnam County had expected the advertising program to generate about $50,000, but are still waiting for their first dollar.

In Massachusetts, the school board at Chelmsford Public Schools is considering a plan to place ads on the exterior of school buses in hopes of generating $100,000 to $160,000 in annual revenue.

The district, which operates 29 school buses, had had to cut 25 teaching positions in the past three years because of budget shortfalls.

Supt. Richard Moser backs the plan, but only because of the tight budget. “If we were not experiencing financial difficulties, we wouldn’t be here talking about [bus ads],” he said at a recent board meeting attended by parents who were protesting the proposal.

The parents said children are already overexposed to commercial messages and added that the ads could distract other motorists and cause accidents.

Under state law, the ads would not be allowed to cover more than 25 percent of the vehicle’s exterior and would have to be placed below the side windows. In addition, no ads for alcohol, tobacco, drugs or gambling could be accepted.