Children whose parents shout at them to "stop playing on that computer" may soon have the ultimate response - proof that computer games improve school results.

Oxford University spin-out company Mindweavers has carried out randomised, controlled trials, to show the benefits of its computer games package, Phonomena.

Phonomena is used by speech therapists to help children distinguish between different sounds - a first step towards pronouncing words so they can be understood by others.

It proved a big hit at St Andrew's School in Headington, Oxford, where children's "word listening ages" or phonological awareness - the strongest predictor of reading, writing and spelling success - shot up by 2.4 years after just six hours use over a four-week period.

A control group which did not use the phonics-based software showed no improvement.

The software is soon to be marketed directly to parents. Mindweavers was set up by Prof David Moore, of Oxford University's department of psychology, who now specialises in helping children with hearing difficulties.

It recently merged with Brainboost, a company set up by Oxford don Baroness Susan Greenfield to develop a computer-based test for Alzheimer's.

Next month it will launch MindFit - computer games to protect ageing brains - at the House of Lords.

Chief executive Bruce Robinson said: "It assesses, trains and has been proven to improve a range of abilities known to decline with age."

He believes brain exercises could be an alternative to drugs for early-stage Alzheimer's. Mindweavers has developed activities for patients with mild cognitive impairment and early Alzheimer's called MindWorks, which is currently in clinical trials - funded by £558,000 from private investors.

He said the games were designed to be fun. "It's just like having a personal trainer. They give you a series of exercises and then re-test you and modify the exercises to suit your level."