(CNN) Teachers at all but three of Detroit's 97 public schools called in sick Monday in protest after finding out they may not get paid after June, officials said.

The mass sickout by more than 1,500 teachers forced 94 Detroit Public Schools to be closed Monday, school district spokeswoman Michelle A. Zdrodowski said. Teachers learned over the weekend that the district would run out of money June 30, according to Ivy Bailey, the interim president of the Detroit Federation of Teachers.

More than 500 people attended a rally in support of the city's teachers Monday morning outside a school district administration building, according to Nikhol Atkins, a staff member at the teachers' union. Teachers and some parents are urging Michigan lawmakers to pass a $715 million education reform package that would fund salaries for July and beyond.

"There's a basic agreement in America: When you put in a day's work, you'll receive a day's pay. DPS (Detroit Public Schools) is breaking that deal," Bailey said. "Teachers want to be in the classroom giving children a chance to learn and reach their potential. Unfortunately, by refusing to guarantee that we will be paid for our work, DPS is effectively locking our members out of the classrooms."

A solution to the school crisis isn't happening fast enough for Detroit parent Tony Kinsey, whose sons attend 11th and 9th grade.

"I support the teachers on getting a fair deal. They're educators," he said. "I'm frustrated with the adults, the leadership. Our children are the ones suffering."

A district in crisis

Detroit's public schools have been in crisis for months. The school district has about $515 million in operating debt, the governor's office has said, and is spending about $1,100 per student on debt service annually. Michigan state Sen. Goeff Hansen has introduced legislation to help bail out Detroit's schools, his spokesman Peter Wills said Monday. That bill passed the Senate and is now before the House, Wills said.

Monday also is not the first time Detroit public school teachers have protested by calling in sick en masse. In January , teachers staged a sickout to protest dilapidated and dangerously unsanitary conditions -- including rat and roach infestations, black mold and pieces of ceiling falling -- forcing the closure of dozens of schools. Teachers also threatened in March to hold another sickout.

District official Steven Rhodes believes the sickouts aren't necessary but is sympathetic to the teachers' plight.

"I am on record as saying that I cannot in good conscience ask anyone to work without pay," said Rhodes, a retired bankruptcy judge who was appointed in February by Michigan Gov. Rick Snyder to be the transition manager for Detroit Public Schools while lawmakers try to bolster the state's largest school district.

"Wages that are owed to teachers should be paid," Rhodes said. "I understand the frustration and anger that our teachers feel. I am, however, confident that the legislature will support the request that will guarantee that teachers will receive the pay that is owed to them. The (union's) choice for a drastic call to action was not necessary."

"I have been and remain confident that the Michigan legislature understands the urgency and importance of the reform legislation that is before it," he added Monday. "The future of Detroit is as much at stake here as the future of the school system."

Kids 'aren't getting what they need'

Sharlonda Buckman, CEO of Detroit Parents Network, an organization of parents with children in all city schools, said she felt an "instant splitting headache" when she heard about the sickout.

"This is one of the most tumultuous school years our kids have experienced," she told CNN. "They aren't getting what they need. It's disturbing. First in January ... (now) we're in May and this is still happening."

Buckman has nieces and nephews in the public school system. She points out that not every parent has the flexibility to stay home from work or to be late when faced with closed schools, and for some that means children are babysat by older children or left entirely alone.

"This creates a safety issue when you have unsupervised children," she said.

It's also a challenge for parents like Kinsey, who works from home but has had to interrupt work three or four times to cajole his sons to do schoolwork. His 11th grader needs to prepare for the SAT, he said.

"I gave them a couple choices, as long as it was learning," said Kinsey, who gave his sons reading assignments. "They think this is a vacation. My oldest wants to go to the movies and the mall. It's been a lot of negotiating, going back and forth and empathizing with them. It's been tough."