"It's a question of minimising risk where possible, in order to keep as many students in school as we can"
I doubt we can minimise risk in any meaningful way with Omicron with cloth masks or similar. Think of the outbreaks where fully vaxxed people with negativ lft's went to parties/ bars etc then a week later over two thirds tested positive. We also know prior delta infection is not very protective against infection with Omicron.
We have kids in primary not vaxxed at all, secondaries where about half of kids are. It will likely spread through pupils and staff quite quickly. This half term will be very disrupted and maybe settle down after that.
Unless/ until the next variant comes along I guess !