Mr Connolly had also been head of English at Belfast Royal Academy, a diocesan lay reader at Helen’s Bay Parish church and chair of the Helen’s Bay Players drama group.
Details of his funeral have not yet been released.
Sam Wolfenden, a teacher at Bangor Grammar School, said that Mr Connolly appointed him to the History department in 2003 and made him head of History in 2009.
He paid a glowing tribute to the former principal: “No-one who worked in or attended Bangor Grammar School in the early 2000s will ever forget the example of Stephen Connolly.
“He was a fine headmaster but he was so much more. He was a model of integrity, an inspiration and a mentor, to staff and students alike.
“That he did not get to enjoy more of his retirement is heartbreaking, but I hope he knew how many lives he changed, how many people measured themselves against the high standards he set, and were better for it.
“He was a compassionate, humane and decent man - a leader in every sense.
“Floreat Bangoria. Deo laus et gloria. (part of Bangor Grammar School’s song in Latin which is translated as ‘May Bangor flourish. To God be the praise and glory’).
Chair of Helen’s Bay Players, Anna Phipps, was full of admiration for Mr Connolly.
On behalf of the drama group she said: “Stephen had been a member of Helen’s Bay Players for more than 30 years. He was a hugely accomplished amateur actor whose versatility and expertise lit up any play in which he performed. He was willing to turn his hand to any role, ranging from an incompetent police inspector in farce, to the Earl of Tyrone in Brian Friel’s Making History. He had developed a wonderful rapport with Helen’s Bay audiences.
“But Stephen gave the Players so much more, drawing on his vast knowledge of English literature, whether he was orchestrating the annual poetry evening or producing extracts from Shakespeare introduced with his natural erudition that made it easily understood.
“He will be hugely missed, by the members of Helen’s Bay Players, by other drama groups with whom he performed and also by the very many theatre-goers who knew they were guaranteed a grand evening’s entertainment if Stephen was in the cast.
“The Players extend their deepest sympathy to Jane, their son Edward and the family circle.”