1. My birthday is in March, so I was 15 when I started high school.
2. I was born in December. That would have made me 14 when I started.
3. I believe everyone is 15 when they start high school, aren't they? I could be wrong.
4. I haven't started high school yet. I won't attend high school until I am 15. That is still 2 years away.
5. I turned 15 the week before my first semester of high school.