Some children are excited on the eve of the first day of school, others are nervous. Essentially, they're feeling the same emotion, it's just manifesting itself in different ways, says Catherine Hutter, pediatric psychologist at St. Louis Children's Hospital.

The kids who seem upset or nervous are probably experiencing mild separation anxiety — which is completely normal, Hutter says.

"Developmentally, we expect children to be able to separate as they get older. They weather separation anxiety at 2, again at kindergarten, and it can happen older — especially if they've been with you all summer, it might come up again," she explains.

She adds: "The first day, seeing a new teacher and a new class, can be tough."

Two things parents can do to calm nerves and help foster a pleasant transition are to help make them familiar with the school and to get them to share their thoughts.

"Talk about fears with kids," advises Hutter, who specializes in anxiety disorders. "Some second graders will have legitimate issues. They might have heard a rumor about the second grade — either that second grade is really hard or that they should know multiplication when they walk in the door."

But, she cautions, while some apprehension is typical, parents should note if the jitters seem out of sync with the child's personality. If the reaction is new or much more severe than normal, it could be a sign of other things.

"In that case, a child could be reacting to something that happened in the family over the summer that leads to an unwillingness to leave the family or to venture out. The most obvious thing would be a divorce, and the child wonders 'Will Mommy and Daddy be OK?' "

Children take their cues from parents, says Hutter. If parents seem to be stressed out, their children pick up on that. "Don't talk about how much you're going to miss them," she says.

Instead, make trips to the school playground with your children in the last days of the summer break. Most teachers start setting up their classrooms a week or two ahead of time, and many welcome new students for a brief getting-to-know-you visit. "Visualization really helps. ... Try to find out the schedule of the day, what are lunches like. The more details kids have, the better," Hutter says.

An upcoming episode of "Sesame Street" will deal with separation anxiety, putting familiar faces into situations that the viewers themselves will soon face. It features Shirley Jones as the teacher at Storybook Community School and airs on Sept. 5.

Children benefit from seeing their favorite characters navigate through problems, says Josh Daniel, co-executive producer and executive editor for the PBS Parents Guide to School, which launches Sept. 1 on the PBS Parents Web site.

"From this content, kids take away the positive idea that 'I can do it, too,' " Daniel says.

Lawrence Cohen, a Boston-area psychologist specializing in children, also suggests parents play school with their soon-to-be students. "Pick up a doll or action figure and say 'Bye, bye. I'm going to my new school,' and see where that leads you.

"In the early part of children's lives, they're busy building up a sense of safety with the people closest with them, and most children develop a pretty strong sense of safety. Children have to learn to extend that sense of safety to the next step when Mom and Dad aren't there. Some kids will breeze through it and some will have a hard time with it," he says.