In the greater Dublin area four-out-of-ten pupils who are driven to school live within 2km, according to a Dublin Transportation Office survey.
The research involved almost 150,000 students.
It found that the numbers being driven to school had increased by 6% over the past five years.
And it found that 40% of all pupils in the region now travel to school by car.
That rises to 50% when it comes to primary school children.
The survey also found a significant drop in the proportion of students using a bus to get to school or college.
That figure was down from 23% in 2002 to just 18% now.
Only 5% of second-level students now cycle to school, and 2% of primary school pupils.
The DTO says parents said distance as the reason for not walking to school with their children, while others said road safety was an issue.