It comes after Premier Gladys Berejiklian said the original plan for students to go back from 25 October was under review because NSW was tracking towards the 70 per cent double-dose vaccination coverage target faster than anticipated.
There are reservations about expediting the return to the classroom with NSW Secondary Principals' Council concerned about teacher shortages.
"The return to school must be based on advice from @NSWHealth, must be controlled and safe for our students and staff," it tweeted.
"Our staff must have time to prepare for any switch from Learning from Home to face to face. We need time for staff and eligible students to be fully vaccinated."
The Independent Education Union is concerned about a lack of consultation and believes the former staged plan was the safest option.
IEUA acting secretary Carol Matthews told AAP the union had not been consulted and there was a lot of "nervousness" given how contagious the Delta variant is.
"I don't think people will be ready for those dates to be adjusted," she said.
Meanwhile, the deadline for health workers to have had at least one COVID-19 vaccination is here. Those who haven't will be forced to take unpaid leave.
Health Minister Brad Hazzard said 97.5 per cent of the NSW Health workforce would be vaccinated by Thursday.
"If you don't care enough to get vaccinated and look after your colleagues, if you don't care enough to look after your patients, then you probably shouldn't be in the health system," he said on Wednesday.
Some 863 new locally acquired cases of COVID-19 were diagnosed across the state in the 24 hours to 8pm on Tuesday, and a record 15 deaths.
Visits to aged care homes will also be allowed from 11 October with two fully vaccinated people able to visit a resident per day.
Meanwhile, the town of Oberon has been placed into lockdown for one week due to an increased risk of COVID-19 transmissions.
The stay-at-home order applies to anyone who has been in the Oberon local government area from 20 September.