Now that your kid has turned 18 you need a new parenting mindset. If your child is a high school senior, she's either 18 years old now or will be soon.
Are most people 18 years old when they graduate from high school in the US? Senior age 17 going on 18. Senior age 21 going on 22.
Twelfth grade, senior year, or grade 12 is the final year of secondary school in most of North high-school. Twelfth-grade students tend to be 18 19 years old.