More than a dozen schools in Tin Shui Wai suspended classes on Wednesday in light of a power outrage caused by a fire the night before.
But some parents complained that the announcement came too late, with their children already arrived at school or on the way.
An announcement to suspend 11 schools was made before 7am. Three more schools were added to the list about an hour later.
The schools were told to look after students who might arrive.
The Education Bureau said it had paid close attention to how the power cut had affected schools. A spokesman said power had returned to some schools while other remained affected, and officials had tried their best to stay in touch with principals and update the list as quickly as possible.
One of the 14 schools that was suspended, the HKFYP Lee Shau Kee College, moved its classes online.
The principal said students who lost their internet connection were told to study at home and report their learning later.
He also said teachers were planning to ask students to share their feelings about such a rare incident, and how they had spent the night without electricity.
As for other schools in the district that were not affected, the Education Bureau called on them to exercise flexibility in handling students who arrived late or could not make it to class due to the power cut.