What quarters do high school's look at?

I just got my report card from 8th grade. I did great during the first semester, but after CST's I began slacking off and went from a B+ in English, to a D. A in PE to a C+, B in math to a C+, and a C to a C- in History... Got mail from my highschool saying that I'm in GATE English and Biology but Dad says it's just a probational class, meaning they're gonna test to see if I get A's in those classes otherwise I'm out. Any advice?