It sounds like those friendships have ended. You've demoted the people with whom you went to high school (or they demoted themselves) to longtime acquaintances. I'm not making judgments here: It's clear they let you down, and you'd hoped for more from them-I'm not suggesting you not be hurt, or resentful that they're turning their attention to you now, when they need you.
Ever wonder why you're exhausted trying to maintain relationships with everyone from your high school lab partner to that person you met at a conference three years ago? Here's something that might surprise you: anthropologist Robin Dunbar's research suggests our brains can only handle about 150 social connections, and of those, only five make up our innermost circle. That's right, five.