Is it normal that this is happening in high school?

I'm a senior in high school now, and I know how you feel. It's hard to watch your friends drift away a little bit, but don't forget that you can also be making new friends as well. If your friends aren't making any effort to keep you, find new ones. If they just seem a little more busy because they have met more people but still talk to you, don't worry about it you can do the same. Try not to let anyone drift too far, and stay open to talking to new people. High school is so fun if you let it be. It's definitely different, and a ton of things change in short time, but it's an amazing time in life that you will only have once. Don't be depressed the whole time, and don't let it fly by. Embrace what you have left. I graduate in a few months and I'm so sad that it's almost over!

Sure.

I actually am going through this at the moment, I'm a junior in HS I have left what I thought were my "good friends " for better ones.

It's normal and inevitable. This is just a taste, wait until you get to college, it's like your friends change by the semester, you meet new ones with the changing of classes some stick and others move on. I earned a great close friend simply because he didn't want me walking to the parking garage alone at night, even though we shared 1 class we stuck and years later we are still close. My oldest childhood friend and I are now mending what years of separate colleges has rendered estranged. Cherish what you have but realize it is a stepping stone we must all go through and get a face-book trust it helps...

I'm senior in high school and I'm a lot different than I was four years ago. I'm definitely more mature.

People change in highschool. It is very normal. It is a major time of growing and self discovery for most teens and this will cause people to change a lot of things about their personalities until they find out what really suits them and what doesn't.

Dont worry, that only happens in high school and not in the real world at all.

It's normal and it changes even more after school, good friends are worth making the effort to keep them, so reach out and be the first to make the move of being a great friend

Normally, we form many (not all) close friendships in Middle School and the fist two years of High School that are sometimes long-lasting.
There will always be many people who you know as being friendly, but who are not within your inner circle of friends.
These relationships often change as a result of long-term sexual partnerships (people disappear from the 'scene').
It will become more and more difficult to form these types of trusting relationships, the older that you become.
My advice, is to repair, as quickly as possible, your relationship with your closest friends. Do this by identifying the reason(s) for them drifting away and then resolving the problem(s) with them.

I guess, all my friends turned into sluts.

Is the classic "mean girls"-esque "american high school" thing really true? Does that happen?