Mrs. Dennis:
 
Each child is unique in how they handle out-of-home experiences.  A lot depends on the level of maturity, expectations, and if older siblings have paved the way for certain "adventures"  Fears, anxiety, and separation issues are not unusual at this age.  I would encourage you to ask him what happens when he is in these situations.  Is it fitting in? unfamiliarity? or just new territory such as changing clothes or a new bathroom.  At 9 years old it is not imperative he go on a school trip overnight.  How much are you willing to chance the phone call?
 
Try a positive conditioning.  For a sleep over, go over to the house, what are the plans? show him where he will sleep, change or what bathroom he will use. Make no demands about the date. IF he decides to go, he gets one free pass to come home.  If he uses it, no more overnights for a determined amount of time until you are ready to try again. Some experts would say allow one phone call, I would disagree.  Camps learned long ago that phoning home can make the home sickness worse.
 
Sleep overs are very popular, but he may just not be ready.
 
Wayne Yankus, MD, FAAP
expert panelist: pediatrics