Missouri Teen Arrested After Slamming Girl's Head on Ground During Fight

A teenage girl has been arrested after video surfaced showing her pounding another girl's head into the ground during a fight, and we've learned prosecutors may try her as an adult.

The footage is shocking ... you can see 2 teens in the midst of a nasty brawl Friday near Hazelwood High School in Missouri -- with one of the girls gaining ground over the other, grabbing her head and slamming it into the sidewalk repeatedly once she's on top of her.

The girl getting pummeled appears to go unconscious almost instantly ... and other students around continue to scuffle. It looks like the girl on the ground starts to have a seizure too.

The girl whose head was slammed into the ground is reportedly in the hospital in critical condition. And now we're told cops have arrested the girl they believe did it to her on a first-degree felony charge ... and her case is being handled by the St. Louis County court system.

The D.A.'s Office has said the case isn't on their radar just yet ... because the perpetrator is a minor, and her case, for now, is being dealt with in the juvenile court system.

However, a rep for the St. Louis County Courts' 21st Judicial Circuit tells TMZ -- the minor in custody at the moment has a hearing in a couple weeks ... which will decide if she can be tried as an adult. We're told this could all happen by later this month.

We're told there's a lot of moving parts that would go into that decision -- including what ultimately happens to the girl in the hospital -- but if things take a turn for the worse ... this could be a much bigger deal than the charges she's currently facing.

In the meantime, the Hazelwood School District says that bullying and fighting are key community issues that need to be addressed for the sake of local children.