I kissed a random girl at our school
Did you really? Did you ask her before you kissed her?
No I just went up and did it.
It's totally wrong to kiss a random person without asking them first. You have to get permission before you kiss someone, because if you don't then you're committing assault.
She was with a group of girls and I didn't think it was a big deal.
It's a pretty big deal to randomly kiss girls, you should never do that. I'm sure that will freak most girls out.