For hundreds of thousands of students, going to school causes an anxiety so severe it can make them feel too sick to go to class.

Eighth-grader David Wolfcale has a terrible case of school phobia that began in fourth grade with stomach aches, Denver television news station KMGH reported. A couple of years later, the stress escalated and he became dangerously depressed.

'School Phobia' Crippling For Some Students

His mother, Vickie, knew his fears were beyond normal, so she sought help.

"He stated to me in the car, hysterically crying in front of the school, 'It would be better if I didn't even exist,'" recalled Vickie.

Some call it school phobia, others call it school refusal. No matter what the name, experts say it's real.

"Parents should understand that school refusal is a very common problem," said Dr. Chris Kearney, of the Child School Refusal and Anxiety Disorders Clinic.

School phobia is often associated with separation anxiety in younger children. Older children may have social phobias, or feel academic or performance pressures, making school less enjoyable or even hostile as they become frustrated. Bullying is also a factor.

Doctors say the best way to tell if your child is over the line and entering some bad territory is if he or she is not adapting. When it becomes something they're just not able to deal with it can cause physical symptoms that last for an extended period.

Doctors do stress that the children should go to school as much as possible, and they say sticking to a consistent morning routine can help ease many anxieties. In severe cases, professional therapy and even medication are needed.