Is there a reason they can not walk to school? It doesn't really take long to walk a mile and it is very good for them mentally to get a walk in before and after school anyway. There may be times when inclement weather might make it a little miserable but proper clothes can address that in all but the most extreme cases. I grew up in MT and had to walk about a mile to my elementary school and almost a mile to my High School bus stop. I enjoyed those walks and the time to think it afforded.