In many states a 14 year old can drive on a "learning permit" as long as they are with a licensed driver 18 years old or older.
When my son was 14 he applied for and received a learning permit from the State of Iowa. The State of Iowa requires the applicant to pass both the written test and the vision test prior to receiving the learning permit. The purpose of the permit is to allow the student to "learn" to drive for two years before they would receive their license. This of course gives them a chance to learn all of their father or mother's bad driving habits.
This permit is valid in any state just like your driver's license. Each state will respect the authority of the issuer of the permit just as they do your driver's licence in another state.
Shortly after he received his permit, we went on vacation to Colorado and he helped me drive out there and back. We traveled through the states of Iowa, Nebraska, Kansas, Missouri and Colorado.
You might check with the State of Texas Patrick. They may have a program just like this one. I know Missouri did when I was younger as I had a learning permit was I was much younger too. Of course I grew up on a farm and had been driving tractors and lime trucks, etc. in our farm fields since I was 8 years old.
This may explain my desire to drive through medians. Right D.C. & Annie?