Dan Haelser, who has taught in both the UK and Australia, said that teachers can no longer say they do not have a role to play in personal, social, health and economic education (PSHE) as it effects every aspect of their work.
Earlier this month, the chairs of four Commons select committees wrote to education secretary Nicky Morgan to make PSHE statutory.
Mr Haesler, an educator and writer, told the education technology conference Bett that how attached a student feels to their school is a "very strong predictor of whether a child will suffer from depression”.
“So when a teacher says 'All this PSHE stuff is really not my thing', I am afraid they’re wrong,” he said. “The point is every single one of us is a teacher of wellbeing. And if you ask how important this is, it turns out school belonging is more important in terms of wellbeing than how attached they are to their parents.”
Teaching in the 21st century is about trying to help kids to “connect and belong”, he added.
The educationist claimed that the reason why young people spend so much of their time online is because “it is where they feel they belong”.
And Mr Haesler claimed that young people’s use of social media was increasingly becoming a way to “outsource their sense of self-worth” to their peer group online.
“I would challenge the idea that kids have become this narcissistic bunch who love themselves,” he said.
“When a kid takes a selfie they don’t take one – they take 45 then they choose one, they put it through a filter, they crop it then they post it on Facebook and check to see how many likes it has,” he said.
“And you know what? It’s never enough. Kids don’t love themselves. If they did they would take one and just put it up, or maybe they wouldn’t even do that. They have outsourced their sense of self worth.”
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