Children are becoming stressed about starting school months before term even begins, research found today.
But anxious parents could be to blame, as their anxiety rubs off on their children, according to researchers at the University of Bath.
The study found pupils who appeared shy were often less stressed by starting school than those who had extrovert personalities.
Dr Julie Turner-Cobb, who led the research, said levels of the stress hormone cortisol were found in youngsters up to six months before classes began.
"This suggests that stress levels in anticipation of starting school begin to rise much earlier than we expected," she said.
The researchers measured the levels of cortisol in children three to six months before term started and again as term began.
The study found unexpectedly high levels of cortisol at an early stage.
Dr Turner-Cobb suggested parents may need more support to reduce their anxiety about the experience of school transition.
She said parents who were anxious about their children starting school could be causing stress to their children.
There was a significant rise in cortisol levels when pupils started school.
But the research found children with a more shy personality appeared less stressed than their extrovert classmates.
"More extroverted children had consistently higher levels of cortisol and their levels tended to remain high throughout the day, possibly because their more impulsive nature gets them into more confrontational situations," Dr Turner-Cobb said.