Dr Hilary Jones explained which students are at more risk of transmitting COVID-19 and therefore should wear masks, during an appearance on Lorraine on Monday.
Hilary was speaking to host Christine Lampard amid Prime Minister Boris Johnson's message urging parents to send their children back to school after the holidays.
He said it was riskier for children to not be in school than it was to send them back, with regards to their education, socialisation, and mental health.
Plus, he reminded parents the risk of death in children was 14 in a million, and those who were affected generally had pre-existing conditions.
The seasonal flu is a far bigger risk, but we do not generally worry about that, he explained.
He said that while the WHO recommends children wear face coverings in school, this is global advice designed to include countries including India and Asia where the transmission rate is high.
"What we know is that younger children don't transmit the virus very much, and if they are exposed to COVID-19 they very rarely get symptoms, so they're pretty safe," he said.
"When children get into their teenage years, they are probably transmitting the virus in a similar way to adults.
"So there is a case, though it is not mandatory at the moment in the government's guidelines, for children aged 12 onwards, to be wearing masks in certain school situations."
These situations include when students travel from classroom to classroom, but not necessarily all day while they are sitting in lessons.
Hilary said the coronavirus could be around for two years, like the Spanish flu was before it suddenly disappeared with no real explanation.
It could be that the virus mutated to something weaker, or it could be that we achieved herd immunity, but Dr Hilary said the same may happen for COVID-19.
* Lorraine airs weekdays on ITV at 9am
