Police say the Hamilton schoolgirls hospitalised last week had not taken ecstasy as originally thought but a mix of benzylpiperazine and other controlled substances.
They have charged a mother, aged 38, of one of the girls with possession of a Class C drug.
Her daughter, who allegedly took the drugs to school, has been referred to Youth Aid.
Six girls aged between 13 and 15, were taken to Waikato Hospital last week after showing signs of drug use at Fairfield College.
The girls were isolated from other patients after becoming raucous and two security staff had to keep their behaviour in check.
It was initially thought the round, pink pills with a bird stamped on them were the Class B drug ecstasy, but testing found them to be comprised of the Class C drug BZP and other controlled substances, said Hamilton city area commander, Inspector Rob Lindsay.
"It is likely there will be more referrals to Youth Aid. What this incident has shown us is that a percentage of young people are vulnerable from making wrong decisions and there are consequences from those decisions."
BZP, or benzylpiperazine, is an active ingredient in party pills and possession of it was made illegal in 2008.
Mr Lindsay said police had been working with a number of agencies in relation to the matter including the school, the Ministry of Education and Child Youth and Family.
The Youth Aid referrals was not all about punishment, he said.
"An objective of the referrals is to ensure the appropriate support services are made available to the young people concerned and that this support is ongoing, to do this we will be working with the teenagers and their families to achieve this."
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