He only knows what you teach him. You are teaching him that even when he can't see you, you will always be there for him to come home to. You are also teaching him how important school is even when it's not so fun, that it's okay to enjoy activities away from home, and it's okay to like to come home, too. It's fine to tell him that you'd love for all of your family to stay home together all day, but that's just not reality. I also think that he needs to know that he CAN call home if he needs to, just for reassurance. I talk to my husband several times a day...not because we need to talk....we just like to hear each other's voices. Same thing...
I think you'll find that the more he is allowed to 'need you' the safer he will feel to venture off and discover the world...he'll always know that mom will be there. Of course, that's a big lesson to learn, but it has to start small...and kindergarten is the perfect time to make that adjustment.
~L.