The Government's flagship pupil premium could have a limited impact on the poor children it is designed to help, a charity suggested on Friday.
Under 3% of teachers say they are planning to use the money to allow pupils to teach their classmates and to give good feedback on students' performance, according to a report by the Sutton Trust.
But these are the most cost-effective measures, and if done properly, are likely to boost pupils' achievement, the Trust claims.
Their new report draws on a survey of almost 1,700 primary and secondary teachers, who were asked how they plan to spend the pupil premium money that their school receives.
The premium, a key initiative for the coalition Government, is extra funding attached to disadvantaged children, following them as they move schools.
It is given to pupils who are eligible for free school meals - a measure of poverty - with the aim of closing the achievement gap between richer and poorer youngsters.
The new findings show that 15% of those questioned say reducing class sizes is their top priority for extra spending, with 16% saying they will focus on early intervention schemes.
One in ten (10%) said that more one to one tuition will be the top priority, with 13% citing additional teaching assistants or teachers, and 8% saying pupil premium funding will be used to offset budget cuts elsewhere.
But more than one in four (28%) said that they did not know what the top priority was for spending pupil premium funding.
Just 2% said it would be used to improve feedback between teachers and pupils, with less than 1% saying they will introduce peer-to-peer tutoring schemes.
The Trust said that their teaching and learning toolkit, created with the Education Endowment Foundation, shows that these two schemes, if implemented well, can boost pupils' performance by the equivalent of an extra eight or nine months in a school year.
Chairman Sir Peter Lampl said: "If the billions of pounds allocated through the pupil premium are to genuinely help improve the results of poorer children then we need to ensure that teachers receive the best guidance on what works in the classroom."
This is why the toolkit had been developed, he added.
A Department of Education spokesman said: "We trust professionals on the front line to do what is best for their pupils. We will not tell teachers how to spend the pupil premium, but we will hold them to account for what they achieve with it.
"From September, schools will have to publish information showing how they have spent the pupil premium and what the impact of that spend was in narrowing the gap between rich and poor students."