Hi J.-
I feel your pain! It feels so disappointing and personal when kids lie. It can feel like we've failed as parents, or that our kids are on the road to deliquency, but...
Every kid lies at some point. To keep from getting in trouble, to get something they want, etc.
The most important thing (this is all my opinion, of course) is not to shame the child. That feels icky for them, and they may feel that they are 'bad'. Telling a lie is a mistake, it's a poor choice. Our job is to help the child see that and teach them the better way.
Talk to him about why he tried to take the car to school (he'll likely say, he wanted to show it to his friends, etc. If he says, I don't know, make some suggestions that you can think of as to why he hadn't told you the truth).
Explain to him why his car couldn't go to school (here is the rule about the car).
Give him examples of why rules are important (we hold hands in parking lots to help keep you safe, etc.)
Read The Boy Who Cried Wolf, and ask him questions about it -- why did the boy lie? How did the people feel about being lied to? What happened to the boy when he lied a lot? What do you think about that? etc.
Express your sadness and disappointment that he CHOSE to not tell you the truth (it's important to stress that it's a choice, and you want to encourage him to make healthy ones). Ask him to think about how he might feel if he lies to you?
And...this is hard: check yourself. Do you tell 'white lies' sometimes, like when a telemarketer calls and you don't want to talk? etc. Kids pick up on little stuff like that.
But mostly, don't panic. :) Help him understand the value of truth and following the rules.
Hope this helps...
Ali