Why does that matter so much to you?
They meet residency requirements as the law is written; they aren't taking anything from anyone else; they're not being subsidized.
It does seem that you prefer that they did not go to college at all as you are putting a large financial obstacle in their path.
So, why don't you want these kids going to college?
If your parents brought you out of Mexico or Central America, etc, and you lived in the US for at least 3 years, how bad do you want to leave and go back?
They can go to college in Mexico because they are Mexican citizens. They snuck in here along with their illegal alien parents and you want to reward this law breaking with cut rate college tuition
Deport a few thousand Mexican teenage hoodlum gangbangers who drain US society..... then I might listen to you on letting illegal aliens go to state universities and at bargain rates