The finding raises questions about the Assembly government's pound;11 million programme of installing the devices in every Welsh school, completed in 2001-02.
The Westminster government also wants to install whiteboards, at around Pounds 2,000 each, in every class so teachers can project video clips and educational games.
Researchers from Newcastle university studied 122 primary schools in six English local authorities, visited lessons and interviewed teachers and pupils.
The teachers were overwhelmingly positive about the interactive boards.
Most expected they would improve their pupils' results and nearly all said they had improved the children's motivation.
The children were equally keen. One said: "It's better than the normal whiteboard because on that all you can do is write and draw boring pictures but on (the interactive) one you can do loads of different kinds of stuff and you can play games."
The researchers found that lessons with interactive whiteboards tended to be faster-paced and that pupils would give longer answers to teachers'
In the first year of the study, 2003, they also noticed that the schools which used them performed fractionally better than comparison schools in maths and science tests. However, in the second year there was no difference .
The report said: "It could be that the motivational aspects of the interactive whiteboards and the pupils' obvious enjoyment of lessons may have misled the teachers into thinking that more learning was taking place than was actually the case."
The report said any improvements may have been at the expense of other teaching practices.
Eight out of 10 teachers interviewed said the whiteboards had added to their workload when introduced, although many said they reduced it in the long term.
An Assembly government spokesperson said: "In Wales we have had generally positive feedback on our initiative and anecdotal evidence (including comments from Estyn) suggested that improvements were being seen in terms of pupil engagement. The Assembly government is funding its own research project into interactivity in the classroom, which majors heavily on whiteboards."