The move to end 87 years of single-sex education has begun as planned with the enrolment of 28 female students across years 3 and 4.

One of them, 9-year-old Julia Rose, could not be happier.

Julia attended the infants school at Canberra Grammar from preschool until she reached the end of year 2. Traditionally the school has offered co-ed classes in the early childhood learning years in a reciprocal arrangement with Canberra Girls Grammar School.

That arrangement has now ended with Canberra Grammar allowing its female intake to stay by progressively offering co-ed classes through to year 12. Canberra Girls Grammar School, meanwhile, is still offering places to boys at the preschool to year 2 level, and said it had no plans to reconsider this.

The schools are just a few kilometres apart. But last year, Julia had to leave her male friends, and her big brother Jett, to move to Canberra Girls Grammar for year 3.

"I was sad to leave when I had to go, but I did make new friends at my new school and I had a very nice teacher," she said.

A handful of girls are returning with her. Overall, the new intake includes 11 girls starting year 4 and 17 starting in year 3.

A further 146 girls make up the preschool to year 2 cohort and will, for the first time, have a pathway right through to year 12. Of a total population of 1748 students in 2016, 11.24 per cent will be female.

While the school was still assessing incoming applications, it had received more than 500 between the announcement it was moving to coeducation and Christmas.

Head of School Dr Justin Garrick said the majority of these applications were seeking places for girls although some were for boys, and he confirmed the school had received enough interest to constitute both the year 7 and year 11 female intakes next year as planned.

While still sensitive to a level of unease among some families to the move, Dr Garrick said he was heartened by the overall response to the decision, which he maintained was the correct one to take, not just for the benefit of all students but for the financial stability of the school.

Growth in coming years would be "measured", he said.

Meanwhile Dr Garrick was looking forward to the start of the academic year and "all the enthusiasm and promise it holds for our students and staff".

While Julia and her mother, Tina, said they had only positive things to say about Girls Grammar, there was no question about their move back to Canberra Grammar when the coeducation announcement was made in October, and they lodged their application that same week.

The move, which caused consternation among some parents who say they were not consulted, was exactly what Ms Rose and her husband David Singh had been hoping for – albeit a year too late to prevent some disruption for Julia.

While there were simple conveniences of having two children at the same school, with one pick-up, one calendar, one IT system, one school holiday program, one uniform and one culture, Ms Rose said the issue extended far beyond that.

"Ultimately we love Canberra Grammar School, but we have never held a strong preference for single-sex education. For our family, this decision has been wonderful in that it will provide the children with a foundation which emulates life beyond the school years."

"We want our son and our daughter to be taught at the same school, and to receive the same level of opportunity and education. We see the move as progressive and forward-looking and we are delighted that Julia can return."

When asked whether she was confident that Julia would feel comfortable in one class with ten other girls and the rest of year 4 being boys, Ms Rose said she didn't even question it.

"I know my daughter well, she does not need any special care or consideration in the classroom because she is a girl. As a trained teacher it is my view that in an equal society, all children should simply be treated as 'people with individual characteristics' rather than being addressed according to their gender."

Similarly Dr Garrick said the school would be "sensitive" but not "overly focused" on the gender of its newest enrolments.

"One thing we have done is group the girls into one class at first so they feel they have some critical mass in these early years, but we feel our focus is rightly on each student as an individual."

The large building works program that was taking place on campus over the Christmas break had been extended to upgrading some of the toilet facilities in the junior school. This would extend to the senior school.

As for Julia's 12-year-old brother Jett, who is moving into year 7 this year, he was "really happy Julia is coming back" and he supported the move to co-ed classes.

"I personally am really happy about it. I think girls can bring some different ideas to the classroom and I'm excited to hear what they are."