The written test can be taken at DPS after 25yr old. Between 18 -24 you must do the 6 hr adult education . The driving test can be any age after 16yr old if they have held their permit for 6months. 18yr old or older can take the driving test same day if you have a appointment for driving test and have watch the 1hr impact video. Or you goto a third party driving school
I believe you can take the test until you're 25, but there are so many other changes and requirements now, just check the website before you go.
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