What's almost as bad as suddenly losing large amounts of friends is losing them slowly over time. In elementary school, I had numerous, fantastic friends who shared the same interests, morals, etc. But slowly over time, they drifted away into private groups, leaving me to my own devices. Either I couldn't bear to part with a certain amount of them to join a smaller group, or I was just squeezed out and deserted somehow, because I hardly changed.
It is my opinion that what brought us together in elementary school was the academically talanted program (PAT). After elementary school, that binding force faded away, leaving me with practically nothing.
A sad, unfortunate tale that I do not think is very uncommon.