Headteachers in under-achieving schools are often given "necessarily discreet" support by LEA advisers. As a result, other staff do not appreciate the importance of their input, the study by the National Foundation for Educational Research found.
The report says Office for Standards in Education evaluations of local authority performance might underestimate their contribution.
Schools' expectations of the local authority did not necessarily match those of central government, the foundation found.
Teachers felt that local authority advisers should be more visible in schools and more accessible. Meanwhile, education authority officers believed the practice of intervening more in less successful schools conflicted with their duty to spread good practice and improve the quality of all teaching.
Researchers interviewed 87 education authority officers and 100 teachers, heads and governors in 10 authorities.
More than half of the school staff and governors interviewed believed that every school needed local authority support to improve. Only fve felt that schools could improve without help. However, staff found it difficult to gauge the impact of their LEA's support.
The foundation says: "If there is genuine partnership, it is extremely difficult to disentangle each partner's contribution to success. The pressure is on education authorities to try to develop rigorous systems that can measure their contribution to school improvement."
Chris Woodhead, the chief inspector, said there should be a debate on the role of LEAs in managing schools.
He said on BBC1's Breakfast with Frost last weekend: "Both the Government and the Conservatives are clearly thinking - and thinking hard - about the role of education authorities. We have found some authorities which are performing appallingly badly. On the other hand, we have found some that are doing a good job.
"It seems clear that we have to have a mechanism in place to support schools that are not capable of managing their own destiny, and that we have to have provision of services that heads need."
"The LEA Contribution to School Improvement - a Role Worth Fighting For", by Chris Derrington, is available price pound;12 from the Publications Unit, The Library, NFER, The Mere, Upton Park, Slough, SL1 2DQ