I was also wondering if there could be any bullying going on, it sounds like something is happening to upset him, be aware and check this out , speak to the teachers, ask him pertinent questions , what friends does he have who does he sit with at Lunch time . Good Luck
Is it possible that someone is picking on him? I was 8 years old and in the third grade when I began fibbing to my mom regularly, telling her that I was sick so that I wouldn't have to go to school, because I was being picked on and teased daily. This went on clear through my senior year of high school. The constant bullying and name-calling was just too much, and even though I was a bright child who made excellent grades, it was easier for me to stay at home, where I knew I wouldn't get picked on. Maybe this is what is going on with your son. Poor little boy. Your post breaks my heart. I have a son who is the same age.
How many days now since school has started? What grade is he in? Does his teacher say he quiets down after a while? --In other words how long is he upset?
Not getting enough sleep at night will do horrible things to ones personality. Did the sleep issues began with the start of school or did they start much sooner?
Did he have the same problems last year? Does he have any of last years friends in this years class? What happens at lunch - does he eat alone?
All of these things are important to help us understand what he may be going through. Of course, the most important question is - has he had any big changes to his lifestyle in the last 3 or 4 months?
Look into anxiety
School may be not right for him, but "average" child with no anxiety characteristics should be able to separate at his age, no mattere where he goes (provided that place is safe)....It may be he is feeling unsafe there, bulling etc - look into all the causes...How does he function throughout he day?
School refusal, unfortunately, is not unusual. I might suggest you google the phrase "school refusal" to read more about this issue. Obviously, your son experiences extreme distress at school and you may require professional help to find the reason and treat the issues. Often, anxiety is one the medical reasons for school refusal - but not always. I agree with the above poster that a visit to your family doctor might be your first item on the list. Hope this helps ...
maybe the school is not the right one for him. have you to talked to his teacher? i homeschool my child and it is a wonderful experience. that could be one option. you have to look up the homeschool laws in your state. has he ever been evaluated by a doctor?