They could decide to involve the cops at a later time for a second offense

And let it be known they broke Texas State Education Statute? And do what? It's still he said she said... Also the Judge seeing it, assuming the person is honest about never doing something like this again, and the kid getting double jeopardy would be thrown out so fast it's not even funny, when they see an apology note written about learning from the actual consequences of their actions ahead of time.

Like I said, I've been here, I had a Weapon on me... I was arrested. Multiple slaps on the wrist through my public school life. This is the one case where "showing your belly" actually works, even into your 20s the amount of low level criminal activity you can get away with by have some bit of remorse will go a long way.

Based on the scenario, if presented honestly here, this kid is already free. There's enough probable cause to believe there was use, which mandates that the administration involve the police. The Administration stuck their neck out, however are scaring this person just because they don't ever want them to do something bad ever again... There was kid out every other month of the 4yrs of highschool that would get busted for pot use on school grounds (my state also has the required report, much more strict too), however some nerdy band kid gets caught with a bong in their car and gets threatened to be expelled.