S.B.
Hello L.,
6 years old is a great age to start one of the more coordinated instruments like piano or violin. This is when the child can track visually from left to right (the way you read words in a book) and coordination between the right and left sides of the body is more developed. The trick is to limit the practice time at the beginning, so that it does not begin as a lengthy chore. As long as you keep the practice limited to 5 days a week, 5-10 minutes a day at the beginning (gradually increasing to 15 minutes by the end of the academic year) Find that right teacher that supports this approach. That right teacher will also be able to suggest the age-appropriate materials to use as well. It is important to start using music and visual aids that appeal to a young child.
I am the director of the Myriad Music School in San Mateo, and we support starting violin no younger than 6. THere are other schools of thought out there, but we think this is the right age to start frustration free.
Best of luck,
S.