Head teachers are warning that they may have to send children home to learn if the number of staff absent because of self-isolating rules means they do not have enough teachers in to safely have pupils in school.
In a video posted on social media, headteacher at Halifax Academy Matt Perry said sending children home will be a last resort but - with schools across the country being told they may face a quarter of staff off - he said they are preparing in case they need to revert to temporary remote learning for some year groups.
"There has been a lot of talk in the media about staff absence and what that means," he said.
"I am convinced they won't close schools wholesale, that we won't be going back to full-scale remote learning for every student in school but we may be in a situation where we don't have enough staff to cover every student in school safely and that's what we have to work on.
"Wherever possible, we will keep all students in school. We will put groups together if we need to. We will do everything that we can but if we are unable to cover teachers and classes then we will have to resort to remote learning.
"We will try and keep children in Reception and Phase One in for as long as possible, and the exam years in - so Years 6, 10 and 11 - for as long as possible.
"But if we need to send year groups home, we will. That is really unfortunate and we're really sorry. We will try and avoid that as much as possible but we will be in the same boat as every other school in the country.
"From the information we have been given, we could be looking at up to a quarter of staff off."
In the video, posted on Sunday, he said he already knew of seven or eight members of staff who would self-isolating when school re-opens this week.
"We should be fine for the first week, it's only three days, we should be OK then," he said.
"Should we have to resort to remote learning, we will make sure the best we can that everybody has IT access.
"We will also, wherever possible, have key worker provision for those families and those children in need.
"We'll make sure that no one year group is overly hit than any other year group," he added.
Mr Perry also explained the latest guidelines for testing and self-isolating, what to do if someone in a child's household is showing Covid-19 symptoms and tests positive, and explained the measures Halifax Academy has in place, including CO2 monitors and air filtration systems that the school has invested in.