I don't have any kids so of course I am an expert on what you should do for your kids.
When I was 15 and a 1/2 I started asking my dad about a car. His reply was
mean and cruel, he said I could buy any car that I can afford and that he approves as a decent car. He told me he would give me an interest free loan for that car, but I was going to pay for 100% of all operating costs and maintenance. He payed for the first year of insurance, and of course continued to provide me with free room and board and mom's cooking and laundry services.
I got a 1960 VW bug for $600. 36 HP of tire smoking power. 36 MPG and 20 cents per gallon gas. A fill up would last two weeks and cost me 2 bucks.
I got a job when I was a junior in high school. Right after school I went to work and did not get home until 6:00 PM and 1/2 a day on Saturday. I paid him back for the car in one year. I learned to work on my own car and take care of it. I never once drove my dad's car until I was in my mid 20s and that was for the trunk space I needed.
In all the miles and years I have never totaled a car, or broken a car from abuse. Mean old dad was a wise man after all. He taught me well.