More than half of Detroit public schools were closed Monday after teachers stayed home in what they called a large-scale sickout.

“We don’t have enough school books,” said Burgess Foster, a fifth-grade teacher. “I haven’t had a printer in six months to print out assignments. I’ve seen mice; I’ve heard about the bed bugs.”

The 48-year-old educator stood outside in frigid temperatures on Monday, calling in sick to join colleagues in protest of what they have called “abominable” working conditions across the school district.

Because of the sickout, Detroit Public Schools was forced to close 64 buildings, over half the district – a move that affected 31,000 students, or nearly 66% of the total student population. Nearly two dozen schools were again closed on Tuesday as a result of additional sickouts by teachers.

Fueled by frustration over large class sizes, lack of basic classroom amenities, and dilapidated buildings, teachers waged the sickout – an organized mass absence of work – seemingly as a cry for help, despite the questionable legality of the tactic: Michigan law prohibits government employees from going on strike.

While state officials criticized what they call an “unethical” approach to raising concerns that they contend hurts students the most, teachers have countered, saying the children are already devastated by current conditions in the district, which is facing financial calamity with liabilities of $3.5bn.

“If we were in suburbia,” Foster said, “folks would be hitting the fan.”

Local union leadership did not formally support the sickout. Nonetheless, teachers’ union interim president Ivy Bailey joined the press conference on Monday to deplore teacher conditions.

“We have to do something; we have to advocate for our children,” Bailey said. “And whatever the consequences are, we’re going to have to deal with it. But we have to stop bashing teachers.”

In recent years, boosters in Detroit have pointed toward recent successes in the city’s downtown and midtown neighborhoods, where a steady stream of residents have flocked and an influx of businesses have opened. But the public school district has remained a problem – and priority – for state and local officials. Michigan’s governor, Rick Snyder, has made a $715m proposal to overhaul the failing district in 2016, though it has so far received little support in the Michigan legislature.

And most observers agree the future success of Detroit is contingent upon whether its schools can be fixed.

Detroit’s mayor, Mike Duggan, said he understands teacher frustration, but “our children need our teachers in the classroom”.

“I encourage teachers to end the sickouts and remain in the schools, and I encourage our state officials to move quickly to address these pressing educational problems,” Duggan said in a statement issued on Monday. The mayor said he has received reports on substandard conditions in school buildings, and is expected to visit several on Tuesday.

What he’ll find, according to the teachers’ union, are endless signs of “deplorable conditions”. At Palmer Park prepatory academy, the teachers’ union said, “pieces of the ceiling our falling on kids’ heads and rats run around”. At Thirkell elementary school, there’s a consistent lack of teachers, so eighth-grade students are “housed in the gym and pulled out for instruction in core subjects for only an hour or so each day”.

The description of Osborn high school was more succinct: “The building is literally falling apart.”

The widespread problems were echoed by teachers who spoke with the Guardian at a midday protest outside the Fisher building in downtown Detroit.

Karen Woodward, a special education teacher at Pasteur elementary school, said teachers lack textbooks and computers and the building’s heat “doesn’t work properly”.

“We have to mop and clean our own floors because we only have one janitor in the morning and one janitor in the afternoon,” Woodard said. “It’s ridiculous.”

The current emergency manager, Darnell Earley, who last week called the recent spate of sickouts “very unethical”, said the mass demonstration on Monday “adversely affected” the district’s employees. (Earley was also the emergency manager of nearby Flint when the city started using a local river as a water source, a decision that has been linked to lead contamination in residents’ household water supply.)

“It is counter … to everyone’s efforts to move this district forward when we send the message to the rest of the state and the nation that was sent today,” Earley said in a statement.

Kieya Morrison, a Detroit native and parent of a district student, disagreed.

“It’s wrong for them to provide these kind of conditions to us … they’re trying to emotionally make us accept garbage for ourselves and our children,” Morrison said. “And it’s not right.”

Flanked by her fourth-grade son, Terrence, she continued: “Our kids aren’t afforded equal education as suburban districts. My son … loves to draw, but he’s never, ever – he’s been in DPS since pre-school – had an art teacher, a music teacher. The lunches they feed are garbage. My niece calls it prison food.”

Teachers and activists have also criticized the state’s role in the district’s exacerbated woes. When in 1999 the state first stepped in and overhauled the governance of Detroit schools, the district’s budget carried a $93m-surplus. According to an analysis by the Citizens Research Council, a Michigan-based policy research group, in the most recent fiscal year the district reported a budget deficit of nearly $216m.

An estimated 41 cents out of every state dollar appropriated for students is spent on debt service, according to the council’s report.

Since 2009, the district has been operated by a state-appointed emergency manager with total control of the district’s operations. In that timeframe, Mayor Duggan said on Monday, Detroit schools have lost nearly half their enrollment, endured serious declines in math and reading scores, and ran up “new deficits in excess of $700m”.

Testing the limits of the law

The teacher sickout proceeded despite a Michigan law that precludes government employees from organizing a strike.

Asked by the Detroit News about the legality of Monday’s protest, a spokesperson for Michigan’s attorney general, Bill Schuette, side-stepped the question, instead slamming the teachers’ move: “Staff may have complaints, but not showing up for work hurts the kids and parents, not the administrators. We feel for these families because this is outrageous, no matter where it happens.”

Reggie Turner, an education and labor law attorney in Detroit who previously served on the Michigan state board of education, told the Guardian a sickout on the scale of what happened on Monday is unquestionably a strike.

“An organized withholding of services is a strike, and strikes are prohibited,” Turner said. “So the conduct of these employees is illegal.”

The question, he said, was how the law could be enforced.

“You don’t have a labor union engaged in a strike,” Turner said. Still, he continued, a court could theoretically enjoin the organizers of the sickouts to halt, levying civil penalties that range from fines to potential incarceration.

Organizers “could be held responsible if a court determines that the circumstances are appropriate under the statute”, he said.

Nonetheless, teachers said they need to keep speaking out, even with potential repercussions on the table.

Andrea Henson joined the sickout on Monday – though she acknowledged the school she teaches at, Bates Academy, “is one of the jewels of the city”.

“We’re in a better situation that most others,” Henson said. The 49-year-old has taught in Detroit for 20 years.

“I’m a strong believer that even though our situation may not be as dire as some at other schools, it’s all about having equity in our education system,” she said. “And I’ve always been passionate about teaching … the reason I wanted to be in Detroit is Detroit students deserve awesome educators.”

As the largest district in Michigan, the students in Detroit need to be “better taken care of than what’s been happening as of late”, Henson said.

“I want to stay positive,” she added. “But you get to a point where, if you say nothing, then that makes it seem like everything’s OK.”