I shoulda been tossed on that basis alone. But notice how big a car is, how much kinetic energy it can deliver onto a target, that it carries a flammable substance called gasoline. It is a far, far deadlier weapon than that knife. Why don't the schools have a zero tolerance policy against such deadly things on campus? Because the administrators themselves need to use them, so they're "Reasonable" about it.
Maybe it will eventually be tossed on those grounds, if he has the funds for an appeal. But the cost of that alone is arbitrary tyrannical punishment.