As
>>8 stated, people change at different points in their lives, especially transitional periods such as making the change from grade school to high school. Keep in mind that these feelings you have towards your friends are likely the cause of you unconsciously distancing yourself from them.
Freshman year was difficult for me, I was the only kid from my school to go to the high school where I've just graduated from. I was often depressed, rebellious, condescending, and belligerent. Realize that this is all the cause of the large transition which you're currently going through.
Keep in mind though, that everyone changes, and that everyone has gone through what you're going through now, you aren't alone in it.