As the US celebrated Labor Day on the last three-day holiday weekend of the summer, cases of the novel coronavirus were reportedly rising in 22 of the 50 states, and one reason is the reopening of schools and colleges for tens of thousands of students.

Colleges and universities are dealing with the arrival of students from some places with high infection rates into dormitories and off-campus housing — and some schools are seeing widespread partying on and off campus.

Schools have set up coronavirus testing centers in stadiums, parking lots and gymnasiums. Some, like George Mason University in Virginia, sent kits to students at home and asked them to send back specimens on throat swabs, which were then sent to labs.

Protocols and procedures have been imposed at virtually every school, from daily temperature checks and contract tracing to having students sign pledges to follow masking and social distancing rules or face disciplinary measures, including expulsion.

The regulations are aimed at not only protecting students but also the general public where the schools are located. Those that have in-class instruction, even if on a limited basis, want to avoid going entirely to online instruction or sending students home, losing millions of dollars in revenue.

"For the most part, everyone I've been talking to has a plan. But to quote Mike Tyson, 'Everybody has a plan until they get punched in the face,'" said Scott Schneider, an Austin, Texas, lawyer and a consultant on higher education.

"It's unlikely that any school in the US will come out of the fall semester without a coronavirus case," he said. "So, if the fantasy is, 'We're going to reopen; we're not going to have cases,' despite everything that's going on in both the local community of the institution and where these young people are coming from, that's a complete fantasy."

Though the late-summer heat wave in California has brought triple-digit temperatures to the San Diego area, thousands of San Diego State University students were ordered Saturday to stay in their dorms until Tuesday morning because of an outbreak. The university has reported 120 cases so far.

About 2,600 students live on campus from among 35,000 enrolled at the university. The lockdown order follows a move to online classes several days ago.

In New York, Governor Andrew Cuomo said last week that colleges will be ordered to go remote if they report 100 cases, or if 5 percent of the campus community tests positive within a two-week period, whichever is lower.

"We should anticipate clusters," Cuomo said. "We expect it. We want to be prepared for it."

On Saturday, more than 20 New York University students were suspended for violating school rules. The school, which didn't provide details about the suspensions, tweeted the update after less than a week of in-person instruction, but local television stations showed hundreds of young people partying that night in Washington Square Park — near the school's Manhattan campus — many of them not wearing masks.

By last week, the University of Ohio in Athens said it had opened "dozens" of student disciplinary cases stemming from parties.

Nearly 70,000 students attend the school, and 65 percent of them live outside university housing in nearby apartments and houses. Students must sign a pledge to follow university rules and health guidelines. But the pledge doesn't make any specific references to parties or off-campus gatherings,

"Students are going to party," Matt Benge, a senior at the school, told USA Today.

Reuters and The Associated Press contributed to this story.