Principal Paul Teys said 550 of the 660 senior school students and 340 of the 440 junior school students returned to the campus.

"It verifies our plan," Mr Teys said.

"We asked parents would they send their children back in this current environment, if we were to resume face to face teaching, and parents said they would and they're true to their word."

Mr Teys said the atmosphere was "wild". "There was excitement in the carpark, kindy kids excited to see myself and the deputy," he said. "Parents were waving and teachers were really happy to have kids back."

He said all year 12 students had returned and were now at a "distinct advantage".

NSW state schools will resume remote learning from Wednesday and stagger the return to classrooms from May 11.

Catholic schools will do the same, having resumed learning on Monday.

All schools are open for children of essential workers or with no other care arrangements.

Independent Education Union NSW/ACT Hunter organiser Therese Fitzgibbon said she had only heard of one other school in the state - Sherwood Hills Christian School in Bradbury, which has 134 students - that had returned to normal operation.

"We're uncertain as to why this was necessary, given it's such an unknown event," she said.

"We appreciate the fact the principal met with the union and has put social distancing and hygiene measures in place to ensure the risks are mitigated, however we still think it's a risky decision to have 800 students and 160 staff back on the one day... we hope there is no adverse outcome as a result."

Mr Teys said the Australian Health Protection Principal Committee and Prime Minister's advice that distancing didn't apply at schools meant "we could relax a whole lot of those measures".

Teachers will continue to maintain distance between each other.

"We've done what many schools wanted to do," he said.

"Many schools are part of systems... and they cannot make decisions independent of the bureaucracies."