Is it bad to be in grade 9 when your 17 years old?

No - its better to be in school trying then not doing anything at all. My younger brother was held back a year in school because of a learning disability so he was always a year older then all of his classmates and he ended up graduating with lots of great friends and high grades that he used to go off to college with and is doing great. I dropped out when I was 16. I didn't go back until I was 18 and it took me until I was almost 21 to graduate - I was put into an adult learning center but I was technically a 20 year old still working on grade 10 school work. My friends mom went to college at the age of 42! Imagine that - she was a 42 year old woman doing presentations with a class full of 18 and 19 year olds! Better to do it now then never - a high school education is something you really need to have now a days, your not alone.

It's not bad, but it's different. I knew someone over 20 in grade 12.

Yes its bad.

yes

No. It happens.