An Invercargill principal, fearing for the safety of his pupils, says a new synthetic drug called K2 is the most dangerous legal high on the market.
Southland Boys' High School principal Ian Baldwin is preparing to make a formal complaint to the Ministry of Health about K2, which has side-effects that include extreme anger and high levels of anxiety and psychotic symptoms.
The Ministry of Health says it does not know if K2 includes banned substances or contains synthetic cannabinoids.
Youth services and police are also worried because it is reportedly being used by city school children.
The R18 K2, which is legally available in blueberry and chocolate flavours and comes in attractive packaging, is sold legally for $25 in dairies close to schools and in party-pill stores.
"It's more dangerous than anything on the market; the government needs to act as urgently on this as they did with Kronic," he said.
Baldwin said he found out about K2 this week, and that he intends to hold a special assembly today to warn staff and pupils how dangerous it is.
He advised parents to look out for signs such as extreme, uncontrolled anger and high levels of anxiety.
Other city principals were also concerned, Baldwin said.
Some were waiting on sponsorship to bring a drug sniffer dog from the North Island to schools in the city.
Southland Girls' High School principal Yvonne Browning had also heard about the drug and hoped no-one would sell it to the girls in uniform or after school hours.
"Parents and the schools need to be in partnership and have conversations," she said.
She advised parents to look for signs, which included spending more money than usual and behavioural changes.
James Hargest College principal Andy Wood said it appeared K2 was unfortunately the "in" drug for at-risk children and synthetic drugs seemed to be on the increase.
"I am very concerned if people are selling these to school aged children," he said.
A 17-year-old boy told The Southland Times he had smoked both types and the chocolate flavoured was the worst.
"It made me feel sick and I started having weird psychotic thoughts. I couldn't stop myself from thinking about all the bad things that had happened in my life. I felt real down and it lasted about than an hour," he said.
He knew a lot of school-aged boys who smoked it regularly and it had different effects on each person, he said.
Southland truancy officer Lindsay Thomas said many parents did not know how dangerous the drug was.
Packets had been found in the playgrounds of an Invercargill school and a 13-year-old-girl had boasted to him she had taken it and he had heard of other children taking it, he said.
A youth had been admitted to hospital and others had been violently sick after taking it, he said.
"From what I gather it's much stronger than Kronic and a hallucinogenic. If somebody doesn't act soon, children will get into a lot of trouble," he said.
Sergeant Brock Davis, of Invercargill, said police were working with Public Health South to ensure shop owners abided by legislation and did not sell it to minors.
Public Health South team leader Anne McSoriley said it was holding education sessions with Southland retailers about the drug.
Since August 2011 the Ministry of Health had placed temporary 12-month bans on some substances.
Health Ministry media adviser Kevin McCarthy said the ministry would work with police to discuss any further action, which might include testing, should it receive a formal complaint about the product.
The ministry's website says current legislation has proved ineffective in dealing with the rapid growth in new party pills and other legal highs.
However, Cabinet has agreed to new legislation prohibiting the sale of all psychoactive substances unless approved by a regulator.
Stargate International, which had been involved in synthetic cannabinoid manufacturing in the past, said it "may or may not be involved in the manufacture of K2".