Family Law Attorney
As long as it is just possession (no sale) then the school zone is irrelevant. Possession of 2 ounces or less is a class B misdemeanor (180 days max and $2000 fine) In Tarrant county it is unlikely that you are looking at any jail time time since you have no priors but you will likely have to attend some kind of outpatient counseling. You need to hire an attorney to arrange a plea but you could even get unsupervised probation with dismissal.
If you retain a good attorney and handle everything properly, you are probably looking at a fine + probation. Let me know if you'd like to discuss. I can be reached at 817.305.7170 or firstname.lastname@example.org.
This attorney can be contacted via email at email@example.com or via phone at 817.305.7170. The above answer does not constitute, and should not be construed as, legal advice.
Criminal Defense Attorney
As the other attorneys have said, probation is extremely likely but you need to try and avoid a conviction by seeking deferred adjudication or any available pretrial diversion available to you. Also, if you're a minor a conviction has collateral consequences you'll need to be aware of like a suspension of your drivers license. Good luck and hire an attorney soon.