Denver’s first teachers strike in 25 years opened Monday with scenes of students dancing and blasting music in a high school hallway, word of middle school students who walked away from their building, and frustration from pupils over the quality of their classroom work.

The chaotic and disorganized scenes painted by some students at schools around the city Monday morning was presumably not what district leaders meant when they said school wouldn’t be “normal” during the strike, which will continue Tuesday.

Student-filmed video showed the halls of Denver’s East High School mobbed with jubilant teens Monday morning. The video was provided to The Denver Post by student journalist Elena Katz, a 17-year-old junior at East High.

Students streamed out of East High on Monday morning after they said school officials told them to leave after some exhibited rowdy behavior.

DPS officials disputed that any students were told to leave East High: “No, of course not,” district spokeswoman Anna Alejo said. “A number of students chose to walk out.”

East High School Principal John Youngquist emailed parents mid-morning about the situation.

“We are thankful that all of our students are safe and we are interested in ensuring the continued safety of our students,” Youngquist wrote. “If you are concerned that your student has walked out of school and you have not had contact with them, please contact us right away.”

Youngquist said all students who walked out were welcome to return to school and follow the special strike schedules they were given.

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Word of disorganized scenes were reported at other schools across Denver.

At the Denver Center for International Studies, a number of middle-school students who had been placed in the gym with two substitutes simply left the school after the subs stepped out, one DPS parent told The Denver Post

Alejo, the district spokeswoman, confirmed that parents of children who left DCIS and didn’t return received robocalls from the district. She did not specify how many students didn’t return, but said “most” did come back to school.

Joe McComb, an 18-year-old senior and student journalist at Thomas Jefferson High School, said the school’s typical seven-period day was changed to a five-period day for juniors and seniors, with courses centered on math, English, social studies and science.

“While the auditorium was completely packed in the morning, many students walked out of the school after the first class of the day,” McComb said. “Not many kids are left in school as of 9:15 a.m.”

Matt Pence, 18, was among the students who left East High on Monday morning. He said students were given strike schedules they were supposed to follow for the day, but that the school ran out of copies.

“It was chaotic,” Pence said. “There wasn’t much control. The substitutes were trying as hard as they could, but there was just too many people.”

When schedules ran out, Pence said students were left standing in the halls. So they began blaring music and dancing.

“We were playing Public Enemy’s ‘Fight the Power’ and also some Migos,” Pence said. “It was getting pretty rowdy in there.”

A photo of a schedule titled “East HS Strike Impacted Schedule” provided by student journalist Ben Hamik showed the day divided up into four periods — college and career, English and social studies, math and science, and exercise and electives — with lunch in the middle.

Hamik, a junior, took a photo of the lessons he was given, which included a worksheet that explained how students’ interests could evolve into careers via an image of an ice cream cone with scoops on top.

DPS Superintendent Susana Cordova said the schools she visited Monday were mostly calm and quiet, although some had students following a different schedule than they were used to.

Inside classrooms, Hamik said students were throwing away the lesson plans that substitutes handed out.

“It feels like everything was slapped together last-minute and most students have left knowing they are wasting their time,” Hamik said.

Katherine Logan, a 17-year-old East High School student, said the day did not result in a whole lot of learning, but she stuck it out.

The district previously assured DPS families students would be given “high-quality” lessons for every grade level and content area. DPS spent more than $136,000 printing, organizing and boxing lesson plans for the first two days of classes in the event of a strike.

“The worksheets I was given were very elementary,” Logan said. “There was a lot of sitting around, and it was pretty disorganized.”

Aliciana Dorrance, an East High School 10th grader, described the inside of the school as “so crazy. There’s nobody in class.”

As Pence was leaving his high school, he wondered what was going to happen with the AP statistics test he had scheduled for Tuesday.

“I don’t know how that’s going to work out. I really hope this just ends soon so we can all go back to school,” Pence said.