The Welsh government education minister said the balance of benefits now far outweighs the risk of sending young people back to class, during a weekly coronavirus briefing.
“If the Scottish experience is anything to say, they have seen a significant increase in the number of children taking Covid-19 tests,” Ms. Williams said.
“We have taken into account the lessons and experiences that we are seeing coming out of Scotland and are in close discussion with our healthcare colleagues to ensure that the screening capacity is available.
“When it comes to testing children, all children who have a new cough, new temperature, and continued loss of taste and smell will need to be tested.
“I appreciate that as we move into the winter months, other winter ailments might be mistaken for, but it is absolutely necessary at this point that if a child or school staff member presents l one of these symptoms – it needs to be tested. ”
Ms Williams said if they tested positive, they and their close contacts would need to self-isolate to keep people safe and that the Test, Trace, Protect (TTP) system would be involved in finding them.
But the minister said exclusion from school should only be used as a last resort, if students cough mischievously like a bad joke.
Ms Williams also said that £ 29million was available to local authorities to help them help young people catch up on learning difficulties, after months spent in class.
Currently, heads of the Welsh government are following the advice of the Chief Medical Officer of Wales, who recommends that members of the public over the age of 11 wear masks indoors where social distancing cannot be maintained, including schools and school transport.
But they did not make it mandatory and left the decision to schools and local authorities, which drew criticism.