I am good at math except I’ve had the same math teacher 3 years in a row. From Freshman year to my Junior year. Everything’s too late now and I passed algebra 2 with a D. My junior year really kicked my butt because I had a 2.9 and now I have a 2.8. I don’t know what to do, but I’m taking an AP class next year for my senior year and I don’t know if that’ll help bring up my GPA. Summer school here is only for students who have failed a class. so I’m stuck
Where are you looking to go to college? And what does the rest of the picture look like for you? Remember that this is a holistic process 
Depending upon which schools you are targeting, a D in Algebra 2 is not passing for many schools. You need a C or higher for passing the class. What are your test scores? Home State? Is your GPA of 2.8, your cumulative 9-11th?
Don’t forget that a lot of schools consider the GPA trend as well as the actual GPA. Do you have any circumstances besides the teacher that could account for the grades? What schools are you thinking of?
If all these other suggestions don’t work, you can always go to a community school or an easier school to get into and transfer. I know some older friends that plan on doing that. As long as you work hard and get results, you can probably transfer into a better school after a year or two. And you can still get that GPA over 3.0 if you do well in all you classes and stay on top of your game. Take the AP test too (if it a good option) and if you do well, that would speed up the transfer process.