They're 2½ years from college and not ready yet
They're 2 1/2 years away from graduating high school. Their written usage, punctuation, and spelling aren't that good. If they didn't want to go to college, I wouldn't worry. But they do, and they need scholarships.
You're seeing an artificial deadline and worrying because it's looming. They don't need to go to college at 17. They can wait until they're 19 or 25. They can take time off to explore the world before they become burdened by responsibilities.
That will give them time to mature and play with the skills they have in an adult arena. It will give them time to form a better idea of what they enjoy and don't enjoy in the adult world and what directions they could head in to support themselves.
Preparing for college doesn't take 2 1/2 years. It takes as long as someone wants to spend on it once they set their mind to wanting it. The deadline is what's scaring you. Forget the deadline. Forget the standard timeline kids follow to get into college.
If they want college as a goal, then they will prepare themselves when it comes time. It may take longer than expected, but ... so what? What will be the harm if they enter college at 18 rather than 17?
Even better than college as a goal, is figuring out what they want to explore in their lives. College can be a means to an end, but as a goal in itself, it can be a rude surprise at the end when someone has subconsciously expected college to provide a clear path beyond and it's either set someone on the path of the rat race, or left them at the train station of life with no choice on the destination list that seems exciting and worth pursuing.