You're projecting a lot of negative thoughts and intentions on your old friends. They're 'not very supportive' and 'perhaps even a little jealous', both pretty heavy allegations, yet nothing in your letter lends support to these allegations.
To the contrary, having read your letter to the end, I would hazard that it's YOU who's showing a lack of feeling towards your childhood pals. In fact, I'm not entirely convinced you want to stay in touch with them at all, except perhaps for the sake of nostalgia. Even then, you don't want them to have a very low-key impact on your life - after all, you're ever so busy with your new set of fast friends and your fabulous new social life! Personally, I think 'shared history' alone is a bad reason for staying in touch with people. If you have little in common with these girls and boys from school, if they've done nothing more significant in your life than share a desk with you for a handful of years, then why support the myth that you regard them as friends? Why bother throwing them the occasional bone in the form of a Christmas card or a text message on their birthday. What's the point? You have years of active life ahead of you, decades of chances to make amazing new friends - as time goes on, will you really have enough time or energy to be touching base with every individual you've ever shared a joke with? I imagine not. So consider NOT staying in touch with your school mates. Consider losing touch with these relics from your past COMPLETELY. They're just a dead weight dragging you down, right?
Just one last thing, one final point for you to consider before taking your snub to its ultimate conclusion: when your little sister hooks up with a bad bloke or your dad is taken to hospital with chest pains or your family dog passes away or you're holed up in bed for a week sucking ice-lollies because your wisdom teeth have been ripped out or your adored childhood house is demolished or your gran moves into a home - who will you be wanting by your side then? Who will you be calling on to cook you macaroni cheese when your face is all puffy from crying and you're feeling all of 10 again? What, do I hear you mumble something about childhood friends? Surely not...