The study, published this week, is a boost for the "assessment for learning" technique which is gaining support.
David Hargreaves, former head of the Government's exam watchdog and adviser to Education Secretary Estelle Morris, is a fan.
The study was led by professors Dylan Wiliam and Paul Black of King's College, London. They say tests and targets do not in themselves raise standards and that quality feedback from teachers is crucial.
Six schools in Medway and Oxfordshire tried the techniques in maths and science classes. Parallel classes, often taught by the same teacher, were monitored.
When GCSE results and national test scores were compared, the assessed classes gained the equivalent of just under half a level at key stage 2, just over half a level at key stage 3 and more than half a grade at GCSE.
The findings support an earlier review of 600 pieces of research from around the world, involving 10,000 pupils.