Last Day of School Equals Another Loss

My children know all too well about loss, and being told "we won't see each other any more once school is done," by a beloved teacher is scary and confusing.  Why do people they love and see every day disappear from their lives like that?  It happened before when they entered foster care and lost everyone and everything they knew at home.  Now it is happening again, and I really did not realize how hard my kids would take it.  I am seeing anger and acting out  and even sobbing by some and lots and lots of thumb sucking and attitude from another.  Cassia could not remove her thumb from her mouth when I went to pick her up today, the last day of preschool.  She doesn't understand what a school year is or why summer break is so great.  She just knows that her teacher has explained very clearly that they will no longer see each other or any of her friends.  She understands loss in the depths of her soul, and she is feeling it.  Man, this parenting hurt kids can be tough.  No matter how much love we give, there are places way deep down that have been formed and changed based on what they have experienced.  I can never take away the pasts of my children, and I cannot always predict the ways or times when it will come out in them.  Right now my kids are hurting.