I did really well from freshman to senior year first semester. But my grades significantly dropped in my second semester of senior year. do colleges really look at it though?
Schools will provisionally admit you and have conditions you must meet to keep your acceptances. If you fail to meet these requirements which means mainly keeping your grades, you could face the chance of being rescinded. Yes, Senior grades 1st and 2nd semester are important.
I mean i only did bad on my first marking period of my second semester. i can still make it up on my 2nd and 3rd marking period right?
If they only require proof that you graduated, you’re fine. If they accepted you expecting that you would keep up your grades, there might (might!) be a problem. Check out your admissions requirements.
But second semester isnt over yet,does that means i still have a chance? 
@Maxtc1: The rule of thumb is no D’s or F’s. Some schools have GPA requirements also, so you need to check your provisional admit requirements for each school.
Yes of course! They will be looking to make sure there are no C/D grades. A slip one quarter, raised by year end is not a big deal. Don’t worry about it.
How was your midyear report? How many marking periods do you have in a semester? Will it average out at the end? If so, you shouldn’t worry. Colleges expect some senioritis after the college application season, as long as the drop off is not too much.
Yes, they look.
ok i got it guys! thank all of you for the help! really appreciate you took your time to help me 