Now an average day begins at 7.30am with breakfast duty and ends at 11pm.
"I felt state sector paperwork and bureaucracy, as well as class sizes of 35 or so, were stopping me teaching, and I wanted more flexibility," she says. She feels the most important difference is the extra-curricular life, societies and clubs. "Collingwood had some of that," she says. "Here, you have to be involved."
However, Rosie misses things about her old school. "Though they had many able pupils, it was especially satisfying to help the ones who were struggling.
"Each school has its own challenges and rewards," she says. "An independent school owns your body and soul."