Fifteen lessons learned during six years of work to narrow the Pupil Premium attainment gap have been published.

These range from the problems of relying on catch-up schemes to the high success rate of strategies involving targeted small-group intervention.

The 15 lessons – which cover primary and secondary schools – also include old favourites such as the importance of effective teaching assistant deployment and high-quality first teaching.

It comes as part of a new analysis from the Education Endowment Foundation (EEF), which says that on current evidence there will be little change to the size of the Attainment 8 and Progress 8 gaps over the next five years.

However, there is hope that secondary schools can still make a difference and the report does predict that the attainment gap in English and mathematics will narrow by 2021.

The five-year forecast was undertaken by Education Datalab for the EEF and is based on key stage 2 data, including the prior attainment of pupils as well as evidence of the “significant correlation” between key stage 2 attainment and key stage 4 performance.

The resulting analysis says that improvements in primary schools over the past few years mean that the gap between the proportion of disadvantaged pupils with at least a good pass in English and maths and all other pupils should reduce from 24 to 21.5 percentage points between 2017 and 2021.

However, for Attainment 8 – average achievement in GCSE across eight subjects – there will be little change, with the current gap of 11 percentage points narrowing to 10.8.

And for Progress 8 – progress between key stage 2 and 4 across eight subjects – the gap is set to increase from 14.8 percentage points in 2017 to 15.6 in 2021.

However, the EEF says there is opportunity for secondary schools to act and includes in the report 15 “lessons learned” from it’s Pupil Premium research and grant-funding work over the last six years.

It also says that if the current trend of entering disadvantaged pupils for more subjects that count towards Attainment 8 continues then the Attainment 8 gap might close further – from 10.8 to 8.8 percentage points by 2021.

Among the 15 "lessons learned" is a focus on targeted small-group interventions for those at risk of falling behind, which the EEF says “have the potential for the largest immediate impact on attainment”.

Other priorities should include robust and rigorous evaluation of teaching and learning strategies, high-quality first teaching, good, evidence-based use of teaching assistants, and sharing effective practice between schools, the EEF adds.

However, schools are warned that transition catch-up programmes are “difficult” and instead “we should aim to get it right first time round for all children”.

The report adds: “The EEF evaluated over 20 catch-up programmes that aimed to support struggling readers at the transition from primary to secondary school. Though some were shown to be effective in boosting attainment, no single programme delivered enough to close the gap."

The attainment gap still grows wider at every stage of education – it is already evident when pupils begin school, growing to 9.5 months by the end of primary school, and then more than doubling to 19.3 months by the end of secondary school.

The EEF report reminds us that the gap is not just an issue for schools rated by Ofsted as underperforming. While GCSE grades for all pupils are higher in good and outstanding schools, the size of the Attainment 8 gap is consistent across all four Ofsted categories of school.

The analysis also warns that there is not a simple link between higher funding and increased pupil attainment. Instead it is how schools use their human and financial resources that counts.

Sir Kevan Collins, chief executive of the EEF, said: “Closing the attainment gap between poorer pupils and their classmates is our best shot at improving social mobility. So while it is good to see that primary schools’ hard work is likely to yield improvements in GCSE English and maths in the next five years, the slow progress in tackling the overall GCSE attainment gap shows there is a lot still to do.

“We know the attainment gap is not inevitable – in one in 10 schools disadvantaged pupils’ outcomes exceed the national average for all pupils – so secondary schools can make some important headway in boosting outcomes for the poorest students.

The EEF curates the Teaching and Learning Toolkit of evidence-based approaches to Pupil Premium spending.