I lied and got my teacher fired in the third grade
Why did you do such a thing to your teacher?
I wanted to make myself look like a hero and garner some attention.
That sounds horrible. There are much healthier ways to get attention that don't involve harming others.
It's just a little white lie. I doubt anyone will find out later.
But it's not a white lie, your actions cost someone their job and you don't know how bad of an impact that might have had on them. You should take responsibility for the harm you caused.