Using his YouTube channel, which has 114,000 subscribers, Cua says he has enlisted parents and other volunteers as part of an initiative called "Help Our Next Generation." In a video posted in late October, he talks about seeing pictures of "people who looked like teachers" directing young students to pick up bricks during the demonstrations that roiled Hong Kong last year. These teachers need to have their licenses revoked, he says in the video: "If you're a teacher and you make your students destroy this place for certain so-called political positions, that's something we absolutely cannot accept."
Cua's vigilante initiative has won the support of some pro-Beijing political figures in Hong Kong. Targeting the city's teachers has become part of a broader plan by China's leaders to reform the city's rebellious youth after last year's sometimes-violent pro-democracy demonstrations.
Some 40% of the 9,200 protesters arrested in the period between June last year and this year were students, according to figures provided to Reuters by the police. Of these, 1,635 were under the age of 18. About 100 teachers and staffers from primary and secondary schools were also arrested, according to the city's education secretary.
Alarmed that so many young Hong Kongers showed hostility to the ruling Communist Party and its vision for a resurgent China, the leadership has turned to re-education - a tried and tested tactic of the Party through decades of extinguishing domestic opposition. The aim is to remake Hong Kong's youth into citizens loyal to China.
Interviews with Hong Kong political figures, teachers and school principals, and mainland Chinese officials, as well as a review of new educational materials, reveal that the school curriculum, teaching staff, exams and extra-curricular activities are all in Beijing's crosshairs.
Lau Siu-kai, the vice president of the Chinese Association of Hong Kong and Macao Studies, Beijing's top think tank on Hong Kong affairs, says the first order of business is to turn young Hong Kongers into law-abiding citizens, then instill them with national pride. "Students should be told not to do anything detrimental to the safety and interests of the country," he said. Once that's been achieved, "we want to cultivate a sense of patriotism."
Responding to questions from Reuters, Hong Kong's Education Bureau said that "fostering students' sense of national identity" is a key learning goal, as it is in other countries. National education "aims to enhance students' knowledge about our country's history, culture and development," the bureau said. "As well as their awareness of the importance of national security, thereby developing in them a sense of belonging to the country."
China's Hong Kong and Macau Affairs Office on the mainland and Liaison Office in the city did not respond to questions from Reuters.
The education campaign is a crucial piece in a bigger project – nailing down political control of the former British colony. In recent months, China has imposed a draconian national security law that allows for the stationing of its feared state security agents in Hong Kong, arrested leading pro-democracy figures and delayed legislative council elections.
The government is painting a picture of a "bankrupt" education system to justify drastic changes and accelerate control, said Ip Kin-yuen, a pro-democracy lawmaker who represents the education sector in the Legislative Council. The moves have engendered fear among teachers, Ip said.
In September, a Hong Kong teacher became the first to lose his teaching license after being accused of promoting the city's independence in class. Responding to the move, city leader Carrie Lam said "bad apples" needed to be removed from the education system.
Earlier this month, the Education Bureau revoked the license of a second teacher, saying in a statement that he distorted historical fact in class, including telling students that Britain "launched the Opium War to eliminate opium in China."
In the First Opium War, between 1839 and 1842, Britain took military action after China clamped down on the opium trade in the country, which was dominated by British merchants. The issue is particularly sensitive for Beijing, which views the conflict as the start of a "century of humiliation," when foreign powers colonized and exploited the country.
Ip said in a statement that the teacher had made a mistake, but that the punishment was "disproportionate." The identities of the two teachers weren't disclosed.
"Teachers play a vital role in passing on knowledge and nurturing students' character," the Education Bureau, which oversees the city's education system, said in response to questions from Reuters. "All actions are taken from a professional point of view to protect the interests of students and have nothing to do with politics."
The increased scrutiny of teachers is having an effect. Michael Wong, honorary executive secretary of the Hong Kong Association of the Heads of Secondary Schools, told Reuters that following the imposition of the national security law in June, many principals have come to fear challenges from the government, parents or the public.
The revision, overseen by the city's education bureaucracy, was completed ahead of the new school year. A review of two of these textbooks shows there have been multiple changes. Expunged are sections that might be considered critical of Beijing, or supportive of democracy and civil rights.
* A section on civil disobedience, which referred to the 2014 pro-democracy protests that shut down major traffic arteries in Hong Kong, was deleted in its entirety. And the "democratic camp" is now called the "non-establishment camp."
* References to the Tiananmen student protests in 1989 that challenged the legitimacy of the Communist Party have been removed.
* Gone is a cartoon that raised questions about the election of Hong Kong's leader by a select few, not universal suffrage.
* A section on the rise of a local, Hong Kong identity and Beijing's meddling in the "one-country, two-systems" governing model that affords the city a high degree of autonomy has also been deleted.
The Education Bureau said the recent review of liberal studies textbooks was voluntary for publishers.
Karen Wong, who teaches liberal studies, says she consulted with her colleagues and they decided not to stray from the revised textbooks when teaching about the rule of law, China's political system and other potentially contentious issues. Until now, many teachers have used materials of their own design.
"Now we'll use textbooks more heavily because it's more safe," Wong told Reuters. She said it was unclear "which terms or which words" could spark a complaint to the authorities from parents or students.
The review, the Education Bureau said, was initiated because of "mounting public concerns about the quality and accuracy" of liberal studies textbooks.
Education Secretary Kevin Yeung announced a series of changes to the liberal studies program on Thursday. These will include cutting the course content in half and establishing a list of approved textbooks, Yeung said at a press conference according to remarks posted on the Hong Kong government website.
The authorities are also scrutinising exam questions.
Lau, from the think tank on Hong Kong, said exams need to reinforce content changes to the curriculum, with students being incentivized to give the right interpretations of topics such as China's constitution and Hong Kong's governing model. "You provide the right sort of textbooks and then you provide model answers to the public examination questions," said Lau, who lives in Hong Kong. Students, he added, would then know "which answers can gain scores in the examinations."
For China's leaders, the youth-led protests in Hong Kong contained unnerving echoes of a perilous period for the Communist Party – the student-led Tiananmen protests that briefly shook their hold on power. After crushing the protests, the Party began in 1991 to introduce a patriotic education campaign on the mainland. The main thrust was to constantly remind students of China's "century of humiliation," and the Communist Party's role in repelling foreign powers and restoring national sovereignty.
The project has been incredibly successful, says Zhao Suisheng, a professor at the University of Denver who has studied the education campaign. "In China today, nationalistic sentiments are prevailing among the young people," Zhao said. "That is the result of patriotic education. They gave them only the information they wanted them to have and tried to block all other information."
Until now, engineering that type of groupthink in Hong Kong hasn't been easy. On a 2007 visit to the city, Chinese President Hu Jintao called for fostering a strong sense of national identity among young people. The local government opened the funding tap, allocating more money to national education.
However, there was no immediate payoff in patriotic sentiment. In 2012, tens of thousands of students, parents, and teachers protested the government's attempt to introduce a compulsory national education subject and the government backed down.
A Reuters analysis of government records on funding for national education shows it has continued to rise. In the 2018-19 school year, the government spent $15 million on student and teacher mainland exchange programs and $12 million in grants to 634 schools that have sister schools in the mainland.
But as the wave of protests last year showed, these efforts had little impact.
Implementing patriotic education in Hong Kong will be challenging because the Communist Party doesn't have the "very well-orchestrated, structured and hierarchical system" that exists on the mainland, said Zhao. If the people of Hong Kong have "free access" to outside information and continue to be aware of things like "the international community's positions on Hong Kong," the authorities will struggle to reshape their thinking.
Already, there are signs of pushback. Ip, the pro-democracy lawmaker, is also the vice president of the 100,000-strong Hong Kong Professional Teachers' Union, which has set up a legal fund to help teachers who have been targeted. They have taken on the cases of both teachers who had their licenses revoked.
"If one teacher can be punished in this way, all the other teachers will be afraid of being punished in the same way," he said. "We want people to realize that we are still fighting, maybe in a different way, but the resistance is there."
On the other side of the battle are pro-Beijing Hong Kongers like Cua, the education crusader. Cua, who teaches Chinese at an after-school tutoring centre, said he launched his teacher-monitoring initiative to counter hatred of China and the Hong Kong police and government. Students, he said, need to be informed about the great progress China has made in recent decades. "No matter how much you hate China, you have to first understand China," he said.
Cua says his group asks parents and students for evidence, such as worksheets, homework assignments and recordings, when they receive a complaint about a teacher. If a school is "slow to act" once it has been approached, then they submit a complaint to Hong Kong's Education Bureau.
Asked about the images of students picking up bricks that he referenced on his YouTube channel, Cua told Reuters they were from a video shared on a WhatsApp group during the protests last year. But he said he couldn't recall specifically where the events took place.
Cua, who has a sixth-grade son, said his group is now developing courses that it will offer to schools "to strengthen national education and national identity."
"In the past, what I worried about the most was whether he got good grades," Cua said of his son. "Now, I only worry about his moral character, whether he understands what is right and wrong."