I thought I had the answer to this one, but my efforts didn't work. I sent my eldest son to nursery for three mornings a week from the age of 2, because he had no siblings or little friends around his own age (none of my friends had babies at the same time as me). I sent him there to play with other children, and he loved it. But I think I just made home too cosy and too much fun, because even though he loved his nursery, and school when he started there, he had to be dragged into school screaming, peeled from my side! He just didn't want to leave me, and no amount of preparation would have changed that - he's just an affectionate and deeply feeling child. He's the most confident of my three children, but also the most sensitive. We talked about school a lot, got excited about it, uniforms and new shoes, books and pencils, and he did seem excited - until the moment he had to let go of my hand.
My shyest child is my middle one. He did not enjoy nursery, because at those young ages he had little tolerance for other children (particularly the loud ones), so he made only one or two friends. I was concerned that he would find school difficult, but he surprised me. He went in happily every morning, with no fuss at all.
My youngest starts school next week and I have no idea how he will react to letting go of my hand on the first morning - we'll see.
However, I'm not sure that we need to ease their separation anxiety, do we? My eldest got over his fears, and became stronger as a result. As far as he is concerned the worst that could happen to him has already happened: he's had to leave me. He has learned that he can survive that, and that it's actually not as bad as he expected. I see a strength in him now that I am sure has stemmed from having to go through that trauma - he's not afraid of anything now, because of what that trauma taught him. He tries new things as often as possible now.
Whereas my middle son is reluctant to try anything new. He refuses to put himself through any experience that might make him feel anxious - he avoids things. He won't try any of the clubs that his older brother goes to. If he thinks an experience might cause him a nervous episode he will avoid it - and I think that the reason for that is because he hasn't had to come out of the other side of a good bit of trauma; he doesn't know that it's nice on the other side, and that he'll be stronger for coming through it. He doesn't yet know that feeling of self-pride.