Sutherland Shire Christian School has emerged as this year's biggest mover among the top 100 schools, skyrocketing nearly 200 places to finish at 65th in the school rankings for overall performance in the HSC.

It is the first time in more than five years that the Protestant independent school has cracked the top 100. It ranked 259th in 2014.

It is just one of many gems found outside the usual "who's who" of the top 20, which tends to be dominated by selective schools and high-fee independent schools.

Bowral's Oxley College skipped ahead 177 places to slide in at 89th, up from 262nd in 2014.

Oxley College principal Michael Parker, who taught two Year 12 classes this year, said the school community was "absolutely stoked" with their HSC results.

He said a culture of students sharing the load and celebrating each other's achievements was key to the school's success.

"We talked a lot about how a rising tide would carry all the boats and if they worked well together and created a culture of learning, then they would all benefit.

"It's very easy to just get dog-eats-dog [but] we very much wanted to create them as complete people who will succeed wherever they go," Mr Parker said. "They're just wonderful kids. We're so proud of them."

Six schools – two comprehensive and four non-government - jumped more than 100 places to finish in the top 100 in this year's school performance lists. Balgowlah Boys, which gained 153 places, and Castle Hill, which rose by 102 places, were the only comprehensive schools to feature among the 10 most improved schools of the top 100.

Independent school St Clare's College in Waverley surged 187 places to finish 92nd, up from 275th last year.

St Clare's College principal Antoinette McGahan​ said a strong mentoring culture among staff had helped propel the independent Roman Catholic girls school into the top 100.

"It's reciprocal – mentoring goes both ways," Mrs McGahan said. Teachers at the school ranged from those with less than five years experience to veterans of the profession with nearly four decades'experience behind them. Teachers of all levels could learn from one another, she said.

"Usually you have such valuable experience on your staff, if you can tap into that and nurture it and pass it on … that's when you really start to see them develop."

Sutherland Shire Christian School's head of secondary, Marilyn Cole, who took the helm five years ago, said the school set out to change the culture and was now seeing the result of many years' work. She said the students who excelled in the HSC also took on a wide range of extra-curricular activities.

"They were very involved in fundraising and musicals and mock trials and caring about other students. It's about the bigger picture."