Sustrans, creaters of the National Cycle Network are trying to change parents' ingrained driving habits and encourage them and their children to be active by walking or cycling to school
If you would like to make a break from the daily school run and in so doing, reduce air pollution and your child's risk of being overweight or obese, then this link should encourage, support and inspire you. It has lots of resources and ideas to help motivate you to change your driving to school habit: sustrans
There is a link to a comprehensive report for school leaders which will also be of great interest to parents. It looks at the value of encouraging physical activities of all kinds in school (and out) and explains the huge advantages to children's mental and physical health and development of such activities. See school physical activity