This is a bad idea. The placement of the angled foregrip on that AR makes me think it's a pistol-length upper. This knife handle is functioning as a vertical foregrip, which is a felony without the proper tax stamp. If you bring this knife to school, you're going to be charged with a felony.
He points out in one of his videos how many Flock systems are not fully secure. You can access these systems and check to see if your vehicle was logged.
I once met a guy who robbed a bank with a fake gun. (There was once an article somewhere but this was maybe 12 years ago.) He did some time in prison and he said they gave him the fake gun back afterwards.
They protect their own.