Whangarei campus cop Hank van Engelen said two Whangarei High School pupils, aged 14 and 15, were so wasted their parents were asked to take them home, The Northern Advocate reported.
"Over the last two or three months parents and schools have been telling me about students going to school stoned on a legal high. They're not illegal, and I'm not sure whether Parliament is dealing with it," he said.
Zoe Baird owner of Cactus Liquor in Whangarei, which sold the pills, with names such as Fuel, Avionic, Kaotic and Kinetic, said they claimed to mimic Class A drugs like ecstasy and speed, but made you feel wide awake.
The substances weren't mind altering, and didn't make you want to steal TVs or break into homes, but too many could make people ill.
Pill users included people wanting extra energy at work, going to the gym or just wanting an extra boost.
If Cactus Liquor employees felt someone was buying on behalf of an underage person, or abusing the products, they wouldn't be served, she said.
A Health Ministry spokesperson said any substance similar in chemical structure to any controlled drug is illegal by default under the Misuse of Drugs Act 1975, meaning a number of substances traded as so called "legal highs" such as the substances mephedrone or naphyrone were illegal.
But occasionally, substances with a unique chemical structure were not covered by provisions within the Act and were traded locally as legal highs.
