The deadline to apply to New York City’s public high schools and middle schools was extended Thursday, after the website accepting applications crashed and infuriated parents one day before the paperwork was due.

The last day to file an application for the advanced grades was pushed back from Thursday to Monday, Dec. 5, the Department of Education announced after the tech glitch.

“DEADLINE EXTENDED! Apply to middle or high school by Monday 12/5. Any additional requirements (such as auditions or assessments) are still due 12/9,” the DOE tweeted Thursday morning.

The extra time comes after the DOE’s MySchools website buckled under high traffic Wednesday, leaving frustrated parents unable to load it and submit proper documents.

As fuming moms and dads suffered through the site crash, a message popped up reading, “Traffic is currently high, and you’ll have access to your account shortly. We appreciate your patience.”

The website crash caused at least one working mom, Lindsay Owen, to waste hours at a computer trying to apply during the already stressful and competitive process — which should have taken just a few minutes, she told The Post.

Many parents then demanded the Thursday deadline be extended on Wednesday afternoon.

The DOE had recommended that applications be submitted online but said students could also file the paperwork through a school counselor or at a Family Welcome Center.

In September, the DOE announced it would overhaul its controversial, pandemic-era high school admissions process and return to prioritizing academic achievement when screening applicants to some of the city’s most competitive public high schools.

The DOE didn’t immediately return The Post’s request for comment Thursday.