PPTA president Angela Roberts said she was concerned about the charter school using Kamo High School's facilities when charter schools receive funding equivalent to $28,000 per student, compared with $15,000 per student for a similar-sized state school.
"We don't want these schools, which are being propped up by considerable additional funding, using resources at these state schools," she said.
In a letter sent on May 10, PPTA's Ms Roberts warned principal Joanne Hutt that sharing facilities could go against health and safety laws and would upset teachers who had voted not to support charter schools.
Two weeks later, the school told Ms Roberts that it had decided not to share its chemistry lab with Te Kura Hourua, saying the issue had become a distraction.
Raewyn Tipene of the He Puna Marama Trust told One News the charter school needed to work in a chemistry area and believed there wouldn't be a problem to ask the nearby high school.