Separation anxiety

Thomas has never had separation anxiety at school and all of a sudden it is coming on full force in June!  After no problems all year, Thomas is having a lot of trouble separating this week at school.  He was crying and saying he wanted to go home when I dropped him off on Wednesday.  When I spoke to the SMArt center they explained that this is usually cause by something else like an upsetting event.  I think most of this is due to this stupid circus show at school.  The teacher did tell me that the director is sitting with him and they are looking at books on the floor while the others practice on stage.  When I picked him up he said he liked doing this.  I talked to the teacher about bringing him in to school an hour later after the practice had ended and this was fine with them.   So we started doing this, but it doesn't help his anxiety.  I am pretty sure we will not attend graduation.  It won’t be pleasant for any of us.   I just feel so sad for him and am not sure how to help, but I know I won't give up trying no matter how hard it gets!