A class-action lawsuit filed last week against the cities of Dallas and Carrollton and the agency that runs school buses in the county could pave the way for $30 million in traffic ticket refunds.

The five plaintiffs — David Sewell of Dallas, Joseph Lafreniere Jr. of The Colony, Christe Shaul of Dallas, Maxine Cox of Dallas and Gary Jones of Dallas — claim that Dallas County Schools illegally used cameras on school buses to ticket drivers for traffic violations they might not have committed.

The external cameras were installed in an effort to improve safety and punish drivers who put children's lives in danger. School districts in several other states, including Virginia, Nebraska and Georgia, have similar cameras, usually installed on the arms extended at bus stops.

"That is a tangible improvement in the safety of our children," Larry Duncan, Dallas County Schools board president, told KXAS-TV (NBC 5).

The plaintiffs all received tickets for at least $300, the minimum penalty, for allegedly driving through school bus stop signs. Their cars were recorded by cameras on the buses, but the plaintiffs say they either don't remember rolling past the stop arms or they weren't the ones driving at the time.

Duncan said the drivers are just looking for a loophole to get out of paying their tickets. He told NBC 5 that city attorneys in five cities have reviewed the implementation of school bus cameras and found them to be legal.

"It's more than legal," he said. "It's about student safety."

Dallas County Schools implemented the cameras in 2012, and the money from the tickets goes to the city in which the offense occurs and Dallas County Schools, which receives 87.5 percent of the fines, according to LeDouglas Johnson, lead attorney in the class-action suit.

Roughly 100,000 drivers have received tickets for driving past school bus stop signs since 2012, according to Johnson.

Those figures couldn't be immediately verified, but if they prove accurate and Johnson's clients win the suit, Carrollton, Dallas and Dallas County Schools would have to repay around $30 million in traffic fines.

"They have to refund all the ticket money," Johnson said. "It's so dangerous to make a speculative investment, especially for a government agent to do it."

The ticketing system implemented by Dallas County Schools holds the registered owners of offending cars responsible, but there's no way to prove the owners were actually the ones driving.

Thompson says he has counted at least 23 ways the school bus camera ordinance violates the Constitution, but one of the primary problems is that drivers don't have the same legal recourse as drivers who receive other types of traffic tickets.

Dallas drivers have to pay a $15 fee, and Carrollton drivers must pay $20, to appeal the decision of an administrative judge to a municipal judge, who has the final say.

"There is effectively no review," Johnson said. "A judge can do whatever they want to."

He also said that Dallas County Schools has attempted four times — in 2007, 2009 and twice in 2013 — to get legislative authorization for the cameras, but has failed each time.

"No bill, law, statute, or constitutional amendment has ever been passed that would authorize any local government in Texas to enact camera-enforced school bus stop arm ordinances which conflict with statutorily established 'Rules of the Road' in Texas," the suit says.