Strong subject knowledge is the most important component of being a good teacher, a major education conference has heard.

Experts from some of the world’s best-performing education systems emphasised the importance of teachers having mastery of their subject, even at primary level.

Mitchell Chester, education commissioner for Massachusetts in the US, said improving the quality of teaching was “the crux” of the challenge in schools. And he said subject knowledge was at the core of being a good teacher.

“To become a teacher in Massachusetts you have to show strong subject knowledge. We feel that is an absolutely essential component. How can you be a teacher of mathematics or science if you are not strong in that subject?” he said.

Massachusetts is consistently the highest performing state in the US in national tests. If its results were counted separately in the international Pisa tests it would rank fourth in reading, 10th in maths and seventh in science, compared with the overall US ranking of 17th, 27th and 20th respectively.

Dr Chester, speaking at the Mayor of London’s education conference, said there was still “tremendous variation” in impact between teachers, but rather than identify and remove the weak performers he said the solution was to focus on teacher improvement.

His comments on the importance of teacher knowledge were echoed at the conference by Pilvi Torsti, state secretary for the minister of education in Finland. She said the focus on teacher quality was a key part of Finland’s success, which has led to consistently high scores in international rankings. The country is the top European performer in Pisa’s reading and science tests.

Finnish teachers need a master’s degree unless they are teaching preschool, where a bachelor’s degree is considered sufficient, Dr Torsti said. “Teachers are academically qualified, professional teachers,” she added.

Sir John Holman, emeritus professor of chemistry at York University and a former headteacher, told the conference he recognised the difficulty schools had in recruiting science specialists. But he said specialist knowledge was vital to inspire a love of science in pupils, particularly at primary level.

“The reality is that young people make up their minds about what they want to be and what they want to do in the future when they’re extremely young. It is extraordinarily important what happens in primary school,” said Sir John, a former director of the National Science Learning Centre.

“Good teaching depends on good subject knowledge and excellent pedagogical skills. You can’t do it without being in possession of both.”

Related stories: 

Nicky Morgan tells pupils: study Stem subjects to keep your options open - 10 November 2014

Teachers should not be guides or experts, just ‘friends’  - 13 April 2014