Schools should consider increasing class sizes to free up time and money for teachers to receive proper professional development, education experts have suggested.
Professor Robert Coe, director of the Centre for Evaluation and Monitoring at Durham University, said a debate needed to be opened as to whether class sizes or better teachers were to be a priority in the future.
"Unless there is going to be more funding so schools can employ more teachers, we need to consider how staff can have fewer hours in the classroom so they can undergo proper professional development," Professor Coe told TES at a Sutton Trust and Gates Foundation conference in Washington DC.
"People often say, would you rather your child be taught in a class of 15 or 30 and obviously I say 15, but I would much rather have a really good teacher who is not exhausted and really on top of their game every day and have that teacher teach more students."
Class sizes in Singapore are larger than in the UK, enabling their teachers to attend intensive professional development classes, he added.
Professor Coe's comments come just days after his research showed that teachers who undergo constant and good quality professional development have the biggest impact on student outcomes.
It also follows the government's drive to reduce teachers' workload; teachers in England have one of the longest working weeks in the world.
Allowing larger class sizes is politically problematic, said Brad Jupp, a teacher and education policy adviser to US education secretary Arne Duncan, who told the conference that more research was needed to see if larger class sizes were a viable "trade off".
"We looked at different countries around the world that had larger class sizes than the US and we found that only Japan did," Mr Jupp said. "They allow their teachers more time to collaborate with each other in return for larger class sizes. I am still willing to hear the answer of whether it is a trade off, but we need to explore whether the trade off is worth the payoff."
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