One-to-one tuition is the catch-up intervention teachers turn to when children are lagging behind in normal classroom and small-group teaching. Emboldened by promising results overseas, the New Labour government championed national programmes prescribing step-by-step individualised support. The aim was to boost literacy and numeracy among underperforming primary school pupils.

Twenty years on, one-to-one tuition is a billion-pound industry, with myriad approaches deployed in most primary and secondary schools for pupils requiring more intensive instruction. It can involve a teacher, teaching assistant or other adult and is undertaken instead of normal lessons, or as an intervention on top of standard teaching.

Tutoring has also boomed outside the school gates. A quarter of pupils aged 11-16 report that they have received some private tuition; it is particularly prevalent among pupils from more privileged homes. Four in 10 state school teachers say they have tutored outside normal working hours.

What’s the evidence of benefit?

There is robust and consistent evidence that one-to-one tuition, delivered effectively, can lead to an extra five months’ learning gain for pupils during one academic year. Recent evaluations undertaken by the Education Endowment Foundation have replicated these results in English schools for programmes such as Catch Up Numeracy, Catch Up Literacy and Switch-on Reading. Other approaches, such as Reading Recovery, also have robust evidence. But larger trials have revealed more mixed results, suggesting a focus on quality and effective targeting is important.

One-to-one support is expensive. A term’s instruction for a single pupil will cost several hundred pounds, so schools must carefully consider how it is implemented and monitor the impact.

What should teachers consider?

The best results follow the universal educational dictum: a little a lot, over a limited time, targeted appropriately. Sessions of 30 minutes, three to five times a week, over a term of six to 12 weeks lead to the greatest gains. Evidence also suggests tuition has more effect when explicitly linked with normal classroom teaching. This is important for private tutoring outside school hours: it should complement, not contradict, core teaching.

The quality of teaching appears to be key to effective tutoring: practitioner trumps programme design. Some studies have found that tuition in groups of two or three pupils has been more effective than one-to-one tuition; others have found better results from one-to-one. Given the cost, one-to-two or even one-to-three is worth investigating.

Programmes involving trained teachers have nearly twice the effect as those deploying TAs or volunteers. Professional development, training and structured guidance for practitioners are beneficial, and important for those less qualified and experienced.

Lee Elliot Major is chief executive of the Sutton Trust and Steve Higgins is a professor of education at Durham University. Together, they authored the teaching and learning toolkit, now the Education Endowment Foundation toolkit