The girl's death rocked the Bucklands Beach community.
Kong was farewelled with special messages from her classmates during her funeral at North Harbour Chapel.
Pigeon Mountain Primary School Principal Ian Dickinson also spoke.
"During the time of the funeral, our students will be sharing messages that they have created for Joanna and her family," he said.
The school was devastated and working to support each and every member of its community, Dickinson said.
The school library had been set up as a safe space for children to speak about it.
Pakuranga MP Simeon Brown said the girl's death was a tragedy and as a father of two young daughters himself he couldn't imagine the pain and grief the family must be going through.
"It's been a real shock to the community, there's been a real outpouring of love and concern to the family who have lost their young daughter in these tragic circumstances."
Staff from neighbouring schools Waka Aranga Primary, Farm Cove Intermediate and Sunnyhills Primary have also posted their condolences on the school's Facebook page, with one teacher saying the little girl had been in their hearts and minds.
"Such heartbreaking news, I feel deeply for the family, it should have been lots of beautiful years ahead in our lovely caring school. Such a tragedy. Rest in peace little Angel♥️ Sincere condolences to the family," one person posted.