HONG KONG—Hong Kong’s largest teachers’ union said on Tuesday it would disband, days after it was criticized by Chinese state media and the city’s Education Bureau severed ties, accusing the group of helping to infiltrate schools with politics. The move is expected to deepen concerns over the suppression of opposition groups in the Asian financial hub after Beijing imposed a sweeping national security law on the city last year that has stoked fears about the shrinking space for dissent. Fung Wai-wah, president of the Hong Kong Professional Teachers’ Union, told a press conference the political and social situation in Hong Kong had become “drastic” and the union was unable to find a solution. “It’s a difficult decision, a helpless decision, and a heart-wrenching decision,” Fung said. The union grabbed headlines at the end of July when the Chinese regime’s state-run media outlets Xinhua news agency and the People’s Daily condemned …