Council officers responded quickly, and conducted patrols in the area, but have been unable to locate the dogs.
Animal Management was taking the incident "very seriously" and anyone with information on the attack should get in touch on 09 301 0101, she said.
"We will be speaking with the boy's family as soon as we can to get any more details about the attack."
In a social media post, the school said the boy was attacked by a "tan dog", possibly a red nose pitbull.
"Our student endured a couple of chunks of flesh being ripped from his arm, and was quickly rushed to the hospital.
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"We're not sure who owns the dog/s but it might be best for our students to avoid walking to school via the Preston Rd entrance unless they're with a group or adult.
"Finally, thank you to the teenage boy who acted quickly and responsibly, and alerted our teachers."
Animal Management investigates all reported dog attacks, Fergusson said.
"If anyone witnesses a dog attack they are encouraged to phone us straight away, to report it and supply as many details as possible, including descriptions of the dogs and owners, and any supporting details such as address where the dog was last seen or car registration plate numbers."