I have been thinking about this for a while.
Children (especially younger ones) need school. On the other hand, it does seem unfair that, between half term and Easter, teachers aged 50 and over (or younger and vulnerable) will, in all probability, be some of the most exposed people in the U.K., with the very old vaccinated.
Older teachers (age 50+) should be able to video link their lessons from home with cover teachers supervising the pupils. (This cover could be externally hired in).
Schools should also be made reasonably COVID secure (windows open, mask wearing, bubbles etc), but extreme measures, such as surrounding children in Perspex screens, would not be undertaken, as the risk of those teachers in school catching COVID would not be severe.
There is no perfect solution here, but the DfE needs to be thinking of what schools should look like between half term and Easter end preparing for it now (such as DBS checking lots of young cover supervisors).