The Hong Kong Federation of Students said that about 13,000 students had gathered for the start of the boycott. The mood was defiant.
The last time students in Hong Kong engaged in such a large-scale protest was in 2012, when they successfully argued against the implementation of national and moral education, which some critics said was a form of brainwashing.
Two years ago, the Hong Kong government gave in. But this time, the main target of their strike, the Chinese government in Beijing, is unlikely to be as accommodating.
The students also sent a letter to the current chief executive CY Leung, blaming him, in part, for Beijing's tough requirements for election candidates.
They said Mr Leung had "no excuse" for absolving himself from the proposal announced by the Chinese government.
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