A person 9 years old can take Hunter Education and never have to take it again. A child 17 or under does not have to have Hunter Education but in that case they have to be accompanied by an adult.
When it was started a child had to be at least 12 to obtain the Hunter Education Certification, that got changed to 9 for the Texas Youth Hunting Program wanting it to be open to children as young as 9 years of age.
I did not stay in a Holiday Inn Express lately but am certified as a Hunter Education Instructor and TYHP Huntmaster.
The cutoff age is actually 16, because at 17, a person must have taken and passed the course. A one time, one year deferral is also available that gives the 17 year old an extra year to hunt with an adult without taking the course.
Also, once certified, a nine year old can legally hunt alone. However, it's up to the parent to decide if it's safe for them to do so.