Hong Kong’s education chief has asked schools to discipline any students or teachers who join a planned strike over Beijing’s imposition of a national security law on Hong Kong. Pupils were being “exploited” for the political ends of the labour unions and student activists organising the action, Secretary for Education Kevin Yeung Yun-hung said in a letter sent to all primary and secondary school principals on Wednesday. Such manipulation came at the expense of the students’ interests and prospects, he said. The organisers are planning to hold a referendum on Sunday on the proposed strike and will go ahead if it receives 60 per cent backing. But Yeung dismissed the vote as meaningless with “no constitutional basis or legal effect” and asked schools to dissuade students from joining. Many younger students protested over the now-withdrawn extradition bill and joined the anti-government movement that followed last year, staging rallies outside campuses and staging a mass class boycott last September . “Any teachers taking part in class boycotts advocated by [the groups] are not only deliberately failing to perform their jobs and neglecting their duties but also purposefully bringing politics into schools,” he said. “It is a demonstration to students of an expression of political demands in breach of established rules.” Schools should take disciplinary action and the Education Bureau would “seriously” follow up any cases, he added. Neither should schools accept leave requests by teachers to join in the action. Students should not chant slogans, form human chains, post slogans or sing songs containing political messages at school as that turns them into venues for expressing political demands, he said. “If individual students refuse to comply with the instructions after repeated persuasion, schools should take appropriate counselling and disciplinary actions … to maintain discipline and order,” he added. The spokesman for one of the referendum organisers accused the education minister of creating “white terror”. “Now students are already not allowed to chant slogans or post slogans,” said Isaac Cheng Ka-long of the Hong Kong Secondary School Students Action Platform. “I can’t imagine what it will be like after the imposition of the national security law. The suppression by the government is exactly the reason why students need to make their voice heard through the referendum.” Teddy Tang Chun-keung, chairman of the Hong Kong Association of the Heads of Secondary Schools, said he believed schools would not feel pressured by Yeung’s letter. “After a year [of social unrest], we are rather experienced now in dealing with activities in schools that are triggered by social events,” Tang said. “We have always asked students to avoid taking part in events that they do not fully understand. And our experience is that teachers rarely join class boycotts.” Asked whether he would punish students who joined the strike, he said: “We can also handle students’ problems through education.” But he said schools might have difficulty explaining the national security law to students given it had not yet been drafted. Opposition lawmaker Ip Kin-yuen, who represented the education sector, said teachers should not punish students simply for having views different from the government. “Schools have no responsibility in explaining government policies,” Ip said. “Even [Chief Executive] Carrie Lam [Cheng Yuet-ngor] doesn’t know the clauses of the national security law. How can schools and teachers explain to students?” But Wong Kam-leung, chairman of the pro-Beijing Federation of Education Workers, welcomed Yeung’s letter. “It gives schools very clear guidelines on dealing with the issue, leaving no grey area,” Wong said.