Tens of thousands of girls are hiding signs of “deep distress” from their teachers and parents, a new report has found.

In analysis of data from 15,000 secondary pupils by the company STEER Education, a stark divide between the mental health of boys and girls was revealed, with experts expressing concern that this could be a long-lasting impact of the pandemic.

Online responses from 92 state secondary schools from prior to the pandemic to December 2021 revealed that girls aged 11 were 30% more likely to suffer from poor mental health than boys of the same age.

The growing gulf between boys’ and girls’ mental health looks to be one of the long-lasting effects of the pandemic, with recovery from school closures taking a long time.

By age 18, girls are more than twice as likely to experience mental health issues than boys.

The number of girls who seek to hide their problems from others has also risen, with 60% of girls going to great lengths to hide feelings of unhappiness before the pandemic compared with 80% now.

Girls are currently 33% more likely to experience poor mental health than those the same age as them before the pandemic while boys are 12% more likely to do so.

The data shows that girls’ mental health is most at risk between the ages of 14 and 18.

Compared with 2018, both boys and girls are 40% less trusting of others, 25% less likely to take risks and 25% less able to choose an appropriate response to life challenges.

The findings come as a record number of children have been referred for specialist care for the most serious mental health problems during the pandemic.

Between April 2021 and October 2021, the number of children aged under 18 needing care for issues ranging from self-harm to eating disorders had increased by 77% compared to the same period in 2019.

Simon Antwis, STEER Education’s Senior Education Consultant, said: “Schools are understandably deeply worried by the growing numbers of students with poor mental health.”

He added that “we should be particularly alarmed by the state of girls’ mental health in secondary schools – it is at a precipice and the pandemic has exacerbated a worrying trend we have seen now for many years”.

“The growing gulf between boys’ and girls’ mental health looks to be one of the long-lasting effects of the pandemic, with recovery from school closures taking a long time.

“But perhaps particularly concerning is the number of girls who are now keeping their worries and fears to themselves, making it much more difficult for their teachers to identify them as vulnerable and in need of support.”