As part of the Whangārei school's positive education programme, students were asked to find people in their community who do good for others for no personal reward.
King was one of about 13 good sorts celebrated at the school on Monday for a range of reasons - from ensuring people have warm and dry homes to live in, to donating to the SPCA.
King moved to China from New Plymouth in 1991 but had already visited the year before.
She wasn't sure what she would do there but knew she had to learn the language first so spent two years studying Mandarin.
"While I was learning the language a baby was left at my bike shed. I picked her up and brought her into my home at the university and it was at that point I knew it was to do with babies."
King cared for that baby girl for about eight months until she was adopted.
After finishing her studies King opened her first orphanage - the Home of Heavenly Healing - in Guangzhou and eventually opened two more - the House of Peace in Beijing and the House of Grace in Yangchun.
"Over the 30 years in China I've had 670 babies that go through my hands and have been adopted out all over the world."
During her time at the Home of Heavenly Healing she adopted a young girl named Ruth who is now 21.
"She was one of my children in my orphanage and when she was about 2-years-old I realised I should adopt her. There was something special about her," she said.
Casey visited the House of Grace when he was 2 but he doesn't remember that.
He said his nainai would tell stories of China when she visited. When asked what his reaction was when he heard them, his eyes widened and he was a bit lost for words.
"I'm pretty amazed at some of her stories," Casey said.
King said she was "really quite happy" her grandson thought of her as a good sort.
"I was really delighted because I've been out of the country for over 28 years so for me to be involved in anything with the kids is number one for me right now. I just loved it."
Huanui College students also helped out in the community on Monday by volunteering at Glenbervie Primary School, Puke Kopipi Planting, North Haven Hospice, Puriri Court, Pehiāweri Marae, The Palms, Surf Life Saving Ruakaka and Glenbervie Pottery.