Why can’t I reschedule my child’s appointment? You may have exceeded the number of rescheduled appointments or missed your appointment beyond the valid period. Related articles Why can’t I make two appointments for my child? My child is in primary /secondary school. Why can’t I book appointment at Student Dental Centre? What will happen if I cancel my appointment? Why are the dates not available for my selection? My child has lost his/her referral letter. Can he/she attend the appointment with the Student Health Centre without the referral letter?