NEW YORK CITY (WABC) -- New York City is delaying the start of in-person learning for most students mainly because of a staffing shortage.
They're now hiring 4,500 new teachers, but the principals union says they need 10,000 additional teachers.
And, that is not the only issue.
Exclusive video taken by a teacher at Benjamin Cardozo High School in Queens shows mice and cockroaches inside the Bayside school.
Teachers there say windows won't open enough to provide necessary ventilation.
This comes after the city was supposed to get all schools sanitized over the summer.
Teachers at Cardoza staged a protest before school Thursday morning.
That was followed by a march through the East Village Thursday afternoon with educators who are fed up.
Teachers and parents are frustrated over the teacher shortage that left some students without a teacher during this online orientation week.
"Starting schools a week later without putting any of the protocols in place that are necessary to keep our students safe is not going to fix the problem," a teacher said.
"My stance is that the buildings are not safe, we don't have the funding for teachers, and until all of that is cleared up, it makes no sense to sacrifice our children," a parent said.
There are so many details that have to be worked out and it's the reason in person learning couldn't start for most Monday, including the many schools housed here at the MLK Educational complex.
This building is closed because of lack of ventilation.
Teachers there just learned more details Thursday about where they would be relocated.
NYC Schools phased in-person start dates
On Monday, September 21, 3-K, Pre-K, and early education sites will open including District 75 for special education.
The following Tuesday on September 29, K-5 and K-8 schools will reopen.
Finally, on Thursday, October 1, middle and high schools, secondary schools, transfer/adult schools will reopen.
New York City public schools can only stay open if the COVID positivity rate stays below 3%.
To check that rate, you can follow ABC7's NYC COVID-19 positivity tracker.
MORE INFO: NYC Department of Education
MORE CORONAVIRUS COVID-19 COVERAGE
abc7NY Phase Tracker: