"He has lost the muscle movement needed to swallow."
Kade is being fed from a tube but his grandfather said he can talk and has not lost his memory.
He has a large family and its members are taking turns at being at his side and helping mum Theresa Smart and Kade's 14- and 16-year-old brothers and 9-year-old sister.
"There's always two people with him at night time so if one needs to sleep, the other can take over," Kade's grandfather said.
"And during the day it's the same thing, so we've got someone at his side at all times."
Whoever's there also records everything that's happened in case hospital staff need to know.
Kade's grandfather said the family had received "phenomenal support" from the community.
"On behalf of Theresa and the family we want to say thank you for the fantastic support and we just want to give the community an update on Kade's health."
The PTA at Sacred Heard has set up a Givealittle page, and Kade's grandfather said money from that would go towards the boy's short- and long-term care and to help his immediate family.
They are facing much disruption and cost, particularly when Kade is transferred to Starship.
"They are going to need support, the whole lot of them," Kade's grandfather said.
A 9-year-old boy involved in the incident was spoken to by police, who have closed the case file.
A Ministry of Education trauma team has provided support to the school.
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