An HMIE report, published this week, attempts to distil the best practice of the most successful schools in improving attainment for their poorest-performing pupils.
The inspectors conclude that, of all the teaching and leadership factors involved, "the most important was the quality of the relationships between staff and pupils throughout the school or department. The characteristics of high-quality relationships were mutual respect and trust, high expectations and aspirations, and self-belief: a shared 'can do' attitude".
The report added: "There was also a powerful core belief: everybody matters and people make the difference."
Graham Donaldson, senior chief inspector of education, said: "We need to understand better why it is that some schools can improve attainment in literacy and numeracy for those pupils who have most difficulty in attaining well, and others can't.
"Our research shows that the characteristics of effective practice which make a difference to young people's lives, by equipping them with the literacy and numeracy skills they need, are not necessarily new or innovative. However, over and above that, it is vital to keep in mind that these characteristics should be present in every school, in every class and in every lesson."
The report, Improving the Odds, Improving Life Chances, follows on from the findings of the Progress in International Reading Literacy Study (PIRLS). It showed that, out of 40 countries, Scotland had a significantly larger proportion of high-performing pupils but the third largest gap between the lowest and highest attaining pupils.
The average score for reading achievement was 547 where schools had fewer than 10 per cent of pupils from disadvantaged homes; it dropped to 497 where more than 50 per cent of pupils came from such backgrounds. But Scotland's mean overall score of 527 was said to be "significantly above" the international average of 500.