HONG KONG — The 15-year-old student woke Monday morning, donned his school uniform of white shirt and blue pants, and left the Hong Kong apartment he shares with his parents and grandparents.

But he had no intention of heading to school. He was among the thousands of students boycotting the first day of classes after a summer of sustained protests that have been fueled largely by teenagers like him. 

“My grandparents don’t agree with me, so I had to pretend,” the student, who wanted to be known only by his last name Wu, said at a rally in central Hong Kong he was attending instead of being in class. “I put on my uniform like I was going to school, but came here instead.” 

Hong Kong’s government had been hoping that once school started, the tensions — and occasional violence — that have played out weekend after weekend on the city’s streets would subside. 

Students on Monday, however, hoped to send a clear message that they are not going anywhere and plan to continue to be the backbone of dissent against their government, the city’s police force and Beijing’s influence on their semiautonomous territory. 

Students plan to “escalate” their actions if the government doesn’t meet their demands — raising the specter of even more unrest as Hong Kong’s police force cracks down harder on protests and the city’s government remains unwavering in its refusal to compromise. 

“Things will not just go back to normal just like that,” said one 17-year-old student who gave only his last name, Chan. “If the government does not respond to our demands, there is no way this will stop.” 

Protests have grown in intensity since June, originally sparked by plans to allow extraditions to mainland China. The past weekend saw some of the worst violence on city streets in months, with unprecedented police use of force and huge fires set by protesters. The crisis has unearthed deep grievances in Hong Kong, the most fundamental being the fear that Beijing wants to erode the city’s freedoms and cultural uniqueness.

Chinese state media, meanwhile, have continued to escalate their rhetoric. The state-owned Xinhua News Agency said in an editorial that the “end is coming for those attempting to disrupt Hong Kong and antagonize China.”

A deep rift has also been created between police and citizens as harsher tactics are being used to discourage the protests.

Outside the gates of several high schools across the city on Monday morning, students and alumni in black surgical masks, helmets and respirators linked hands in protest. At St. Francis’ Canossian College, an all-girls high school that counts Hong Kong leader Carrie Lam as one of its graduates, students held up signs that read: “Chief Executive, will you listen to the voices of the younger sisters from your school?” 

At Queen’s College, students placed a hard hat, goggles and a respirator on a statue of Sun Yat-sen, known as the founder of modern China and the all-boys high school’s most distinguished alumnus. 

In a news conference Tuesday, Hong Kong Education Secretary Kevin Yeung said schools “should not be used as places for raising political demands or trying to exercise pressure on the government on political issues.”

“We would like to keep schools as a calm, peaceful and orderly place for students to study,” he added.

Later in the afternoon, tens of thousands attended a rally at the Chinese University of Hong Kong despite a warning from school authorities that their gathering was “risky” and shouldn’t be held. Students packed the center of campus and draped black banners on university buildings, including one reading “Fight for Freedom.” 

Chants of “Liberate Hong Kong, revolution of our time” thundered across the campus, at times completely drowning out the speakers addressing the enormous crowd.

Universities in Hong Kong — which up until this point in the protests have been in summer recess — are expected to be the new battleground for tensions between mainland Chinese and Hong Kongers.

Already there have been clashes on college campuses in Australia and elsewhere in the world between those supporting the Hong Kong protests and those backing Beijing’s stance.

Students from the mainland make up a huge chunk of university students in Hong Kong, and many of them cannot understand why the local students are taking to the street. 

Before the rally at Chinese University, one mainland Chinese student ripped up a protest banner and yelled that he supported the Hong Kong police. “Students should study, not strike!” he screamed, according to a witness.

Almost all of the dozen or so students interviewed by The Washington Post mentioned police attacks and their use of force as a key reason for their continued participation in protests and Monday’s boycotts. 

On Saturday, police stormed subway trains and swung their batons and shot pepper spray at protesters and ordinary citizens cowering in the carriages. Police said they were responding to “violent acts” and vandalism in the stations. 

Police made 159 arrests between Friday and Sunday, they said in a news conference, including at the subway stations. Almost a thousand people have been arrested on charges relating to the protests since June, including dozens on harsh riot charges. 

“My heart is broken from the police brutality,” said Jerry Liu, a 15-year-old student also boycotting class. “Skipping school is nothing compared to our brothers and sisters who dare to go out and fight . . . for our freedoms.” 

The school boycotts coincided with a call for a general strike on Monday and an effort to once again disrupt transportation networks in Hong Kong. The plans however appeared to have limited effect, as officers in riot gear waited at subway stations to arrest anyone who tried to hold doors open. Officers made eight more arrests on Monday morning. 

About 40,000 people joined a rally to mark the strike in Tamar Park, near the Legislative Council building. Some protesters later gathered around government buildings close to a police cordon and were pushed back with pepper spray.

Police also stopped and searched students outside high schools around the city. Officers stopped alumni who were handing out pamphlets and brochures in support of protests outside their high schools, and searched their backpacks. 

“We are not afraid, these are just scare tactics,” said Isaac Cheng, a 19-year-old university student who helped organize a rally for secondary school students. “In our fight for freedom and our fight for democracy, we must overcome our fear.” 

Tiffany Liang and Timothy McLaughlin contributed to this report.