Marchers called for revenge and accused the Hong Kong police of misconduct in his death; security footage has been unable to verify what happened.
He had been in a coma but succumbed to cardiac arrest on Friday morning.
Many teens are worried about having arguments because of political differences and fear being bullied.
The police have yet to determine the cause of his fall, but are seeking additional security footage that may help.
Spokesman for Food and Environmental Hygiene Department says decision made 'in view of the current social situation'.
A man from mainland China also waved a knife at a group of students while singing the Chinese national anthem.
A survey by the Association Concerning Sexual Violence Against Women has found that majority of those who responded did not want to report incidents to police.
The blaze broke out in the early hours of Thursday; about 500 people were forced to flee their homes.
Secondary schoolmates describe Chow Tsz-lok as quiet and friendly and don't know if he took part in any anti-government demonstrations.
Pro-establishment lawmaker expected to undergo surgery for knife wound to his chest.