He will be sentenced on January 26.
Chairman of the Dilworth Trust Board, Aaron Snodgrass, said the school hopes Stephens' guilty pleas are a "step towards justice and healing for his victims".
"We commend the bravery of those who came forward resulting in today's conviction.
"On behalf of the school, we are sorry for the abuse you endured while you were at Dilworth.
"Our focus remains on supporting our community at this difficult time and in particular those Old Boys who were victims of abuse."
Snodgrass said the school continues to engage with police, the Royal Commission of Inquiry into Abuse in Care, as well as working to establish a "best practice redress programme" for Old Boys who are survivors of sexual abuse.
The programme is expected to launch in the first half of next year.
Stephens was one of the latest men to be charged in relation to alleged offending at the Auckland school.
He was charged along with a 39-year-old in early June, bringing the total number of men accused of historical child abuse to 11.
Three men have since died.
At Stephens' first court hearing he did not appear because of physical and mental health issues that were "exasperated" by media coverage, his lawyer Olney said.
Olney said he was engaged with a counsellor and medicated for stress.
Police said they have spoken to more than 150 men who have made allegations of abuse relating to the school under Operation Beverly.
A number of the accused are still moving through the court system.
Dilworth School is considering compensation for victims, the Herald revealed this month.
Stephens' guilty pleas add to a growing list of men who have admitted to offending.
Former vicar Ross Douglas Browne admitted offending against boys from 1987 to 2004 earlier this month. He also admitted to possessing objectionable material in 2020.
Ian Robert Wilson was sentenced to three years and seven months in prison for indecently assaulting five students between 1975 and 1992 - some of them more than once and over a period of several years.
Where to get help:
Dilworth Trust Board chairman Aaron Snodgrass has encouraged Old Boys to contact the school if they need support. Any Old Boy who needs assistance can email assist@dobsupport.com and an experienced psychologist will call you.
NZ Police services for sexual assault victims
Victim Support 0800 842 846
Rape Crisis 0800 88 33 00
Rape Prevention Education
Empowerment Trust
HELP Call 24/7 (Auckland): 09 623 1700, (Wellington): be 04 801 6655 - 0
Safe to talk: a 24/7 confidential helpline for survivors, support people and those with harmful sexual behaviour: 0800044334.
Mosaic - Tiaki Tangata Peer support for males who have experienced trauma and sexual abuse: 0800 94 22 94
If it is an emergency and you feel like you or someone else is at risk, call 111.
