http://news.bbc.co.uk/2/hi/health/5362670.stm

anadian scientists compared children aged four to six who took music lessons for a year with those who did not.

They found the musical group performed better on a memory test also designed to assess general intelligence skills such as literacy and maths ability.

It's quite a lofty conclusion from a sample size of 12. Also, there may be a selection bias here, as parents who want to give their children music lessons may stress education more in general, which would also affect the children's mental development.

Still, like any language, music is best learned at a young age, so if you're going to do it at all you are better off doing it early.

They didn't mention how those children were selected for the study. It might have been random. I'll see if I can find the abstract.

Cool, it is online:
Auditory evoked responses to a violin tone and a noise-burst stimulus were recorded from 4- to 6-year-old children in four repeated measurements over a 1-year period using magnetoencephalography (MEG). Half of the subjects participated in musical lessons throughout the year; the other half had no music lessons. Auditory evoked magnetic fields showed prominent bilateral P100m, N250m, P320m and N450m peaks. Significant change in the peak latencies of all components except P100m was observed over time. Larger P100m and N450m amplitude as well as more rapid change of N250m amplitude and latency was associated with the violin rather than the noise stimuli. Larger P100m and P320m peak amplitudes in the left hemisphere than in the right are consistent with left-lateralized cortical development in this age group. A clear musical training effect was expressed in a larger and earlier N250m peak in the left hemisphere in response to the violin sound in musically trained children compared with untrained children. This difference coincided with pronounced morphological change in a time window between 100 and 400 ms, which was observed in musically trained children in response to violin stimuli only, whereas in untrained children a similar change was present regardless of stimulus type. This transition could be related to establishing a neural network associated with sound categorization and/or involuntary attention, which can be altered by music learning experience.



Fulltext PDF: http://brain.oxfordjournals.org/cgi/reprint/awl247v1?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=Trainor+&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT

It sounds like the study decided who got what sort of training, so I don't think you can attribute it to the parents.

A shame that music programs in schools are becoming so rare these days.