Now just seven of them remain in teaching.
According to a survey of 3,000 recently-qualified young teachers, workload pressures and the impact on teachers' mental health is driving out idealistic young recruits.
The survey by the National Union of Teachers suggests 45% plan to leave within the next five years.
Half of these planning to leave pointed to concerns about their mental health.
But 70% said a passion for teaching  had motivated them to stay, despite working weeks ranging between 51 and 61 hours, according to the survey.
A member of the NUT young teachers working party, Ms Chisholme told how an inspirational young English teacher she worked with at a school in Portsmouth was forced to leave because of the risk to his mental health.
"All he wanted to do was to be a teacher," she said, but in the end he decided his well-being was more important.
She added that she was "sick of seeing all her colleagues being so downtrodden".
"We should be left just to teach and provide awesome opportunities for learning.
"We end up filing endless paperwork, box-ticking, trying to prove we do our job. Maybe just trust us," she added.
Henry Emoni, a maths teacher, said it was his fourth year in the profession and he was already disheartened.
"My mum was a teacher, and I know how hard she worked."
He said teaching had always been a profession in which extra hours are worked, but it was frustrating when much of these were to do with bureaucracy rather than the pupils.
"At various points I've said to myself, 'can I keep this up?'
"What keeps me there is the kids."
A Department for Education spokesperson said teaching remained an attractive profession with more people joining than leaving or retiring.
"We continue to work with teachers, unions and Ofsted to tackle unnecessary workload and challenge unhelpful practices that create extra work, including through an offer of targeted support to schools."
He added that the department was working on ways to improve teachers' career progression to encourage them to stay in the profession.
When Laura Chisholme trained as a science teacher, 36 others qualified alongside her.