I've retained 3 friends from school days, two I met in infants, although we didn't actually connect as friends until the juniors. They both had Irish parents and I spent a lot of time around one of their houses and loved her parents, they had such an amazing, whacky, Irish off the wall way of expressing themselves. Their house was almost a drop in-centre for their children's friends, everyone was welcome, I think subliminally I wanted to model myself on them in some respects. The Irish side of my family is further back and didn't figure so large in my life they were a great introduction to Irish humour.
My other friend and probably I'd say my best friend, didn't come up through juniors with me and the other two, we met at my convent senior school she was one of the protestant fee payers, as opposed to us, the non fee paying catholic rabble who were there courtesy of our parish priest. She and I were often in trouble together, nothing major, impertinence mainly, well at least our nuns version of what they deemed that to be, which could mean anything from showing too much leg, daring to disagree with them, the wrong look on one's face, known these days as "resting bitch face" and depending on which way the wind was blowing and what side of the bed they'd got out of, quite often the wrong side! all in all the most minor transgression could land us in their bad books. I think our friendship started simply because she and I are at one with our sense of humour, often absolutely ridiculous at times, so much so, that our respective children often wondered what the hell set us off, we've holidayed as families together quite a few times, I don't think there's anyone who makes me laugh more than she does and she's said the same about me, kindred spirits and partners in crime! We're always What'sapping each other with nonsense even now and sometimes serious stuff as well.
I've retained one great friend from my working life, so that relationship is nearly 50 years old, she is West Indian well born in Jamaica but brought up here. Again we clicked straight away. She was the first black person I'd met, I've learned a lot from her about West Indian culture, and again she has a wicked sense of humour. I also count my husband's daughter and daughter in law as close friends, we're very close.
I know it's corny, but I echo Kitty, my husband is my greatest friend.