I'm worried about my grades?

I've heard my teachers say that I have the ability to get straight A's- I just need to study more. My homeroom teacher also told my dad that I need to participate more (that's why I'm getting B's and B+'s instead of A's). I'm in seventh grade, and my teacher says that high schools will look very closely at this year. For the most part, I received A's and B's. But also, three C+s. One in science for one quarter, and two in math for two different quarters. For the last progress reports, I got a C in math and C+ in science cause I slacked off. I got really worried so I worked really hard to raise my grades. Unfortunately, the math/science teacher only gave us like 2 grades. So I raised my math to a C+ and she told me that I was ONE POINT away from getting a B- in science. Exactly one point. -_- I'm REALLY worried! And I honestly regret slacking off. Once again, I mostly got A's, A-'s, B+'s, and B's. No B-'s. Except for those ******* three C+s. >_< HELP ME! I wanna get excepted into a good high school, but idk if they'll accept me with my grades. :(