An adviser to the Scottish Government said that Scotland's decline in the PISA statistics, was being replicated in many countries, and the root of the problem could be social media technology.
Professor Pasi Sahlberg, a Finnish educator who works in the University of New South Wales, said that many OECD countries had seen their education systems decline, with the PISA results in maths, science and reading getting worse.
Speaking after a meeting of the International Council of Education Advisers, Professor Sahlberg said that the PISA results - which saw Scotland decline in maths and science but improve in reading - was reflected elsewhere.
He said: "It's not only what the government in Scotland should do, but what the heck is happening around the world with kids not learning in the way they used to? The question should be first, why are young people are not doing any better in these tests than they should do, or used to do?
"What has happened is related to technology that the kids have. The average teenager spends anything from seven to 11 hours a day on technology so what are these kids not doing when they're taking so much time to do things with media and technology? One of the things they don't do is pay attention to what's happening in school and they don't sleep as well as they used to."
Professor Sahlberg pointed to the release today of a government- commissioned study by the University of Glasgow which found that using mobile phones at night is having a negative impact on young people's sleeping patterns and mental well-being.
He added: "There's no question on whether this has an impact on ability to learn in school. It's nothing to do with school education or curriculum or teachers or structures. My bet would be, and we're doing some research in Australia on this, is that this is something that we parents with our children have to stop, because it is making learning complicated and difficult, and we're not feeling so well or as happy as we used to be.
"My guess would be, if we really would like to put Scotland back on an improving course in PISA, then if we can fix somehow this media technology - it's not just a Scottish issue - we would see improvements much faster than doing any other thing."
The Scottish Government has pledged to invest more than £60 million to create 350 counsellors, ensuring that every high school has counselling services by September. It has also pledged to enhance support and professional learning for teachers on good mental health.
Professor Harris said: "The focus on health and well-being of young people is critically important so it's not just about academic achievement. That's an area the Scottish Government are focusing on but more can be done. The challenges for young people are acute and extensive so we can always improve things."
Asked if every school should have a counsellor Professor Sahlberg said: "Absolutely. In Finland today in Helsinki the Parliament is considering this very question, having a therapist in every school, so it shows that its not only teachers who should be dealing with this, and also that teachers increasingly need that support.
"The decline in well-being and mental health is an alarming thing here, and a critical question in many other countries. The schools were not designed to work with so many kids with some type of mental difficulty; teachers were never trained to deal with those challenges."
Professor Harris added: "I would agree wholeheartedly with that. A child who comes to school anxious, upset or hungry, it's almost impossible for them to learn. Anything that alleviates those barriers to learning will get us closer to improving attainment, so it would be a very good move."