Sending pupils back to school full-time next month is "absolutely not a done deal", according to a key member of the Scottish Government’s education recovery group.
Stephen McCabe said there are "serious concerns" in trade unions about protection for teachers.
It comes weeks after Education Secretary John Swinney changed course from a part-time start to schooling to full-time education in the middle of the coronavirus pandemic.
There had been pressure from political opponents and some parents to move more quickly, while others warned against undoing vital public health protection.
This weekend, Covid-19 infections in Scotland increased as the country opens up to travel, tourism and retail.
Meanwhile, teachers on the front line are preparing to enter classes full of children mixing together.
McCabe told the Sunday Times: "There are a number of unresolved issues. The unions want to know about access to PPE for staff and whether there are enough resources available for appropriate cleaning in schools.
"They want to know what surveillance testing there will be in schools, particularly for staff and for senior pupils who appear to be at higher risk than younger children, and there remain issues around public transport and what measures should be taken to protect pupils.
"It is absolutely not a done deal that Scottish schools will go back full-time on August 11 despite the positive trajectory we are on."
McCabe is children’s spokesman for the Convention of Scottish Local Authorities, known as Cosla. He sits alongside Swinney on the government’s Covid-19 Education Recovery Group.
Advice for schools suggests children will not need to observe physical distancing from each other but teachers will need to stay two metres apart. Swinney will confirm progress and further details next week.
A Scottish Government spokesperson said: "The plan to fully re-open schools is dependent on having measures in place to ensure the safety of pupils and staff and we will publish guidance on this soon. We continue, through the Education Recovery Group, to work with teachers’ representatives, local authorities, parent bodies and trades unions as we formulate that guidance."
