We also had a worry about school.  And we both work and are not readily available to drop everthing at a moments notice.  We made the decision that should anything happen that the school had our permission to call 911 first and then contact us.  My son is now 12 and I can reasurring say that we have never had an incident.  We did however have to sign an agreement between the school and ourselves outling what needed to be done and in what order.