Why aren't face shields being promoted for schools?

[Morfin]

I know they are not as effective as masks however they are also much more comfortable and not a barrier to communication. They retain the bigger droplets and dentists have been using them for years pre Covid so must have some benefits. They can be washed with soap and water and are inexpensive.
Why are they not being used on classrooms?

Because they are ineffective without a mask and there is evidence they increase risk especially when worn by a taller person amongst shorter ones (which pretty much describes a teacher-pupil relationship, at least in primary).

They dont work. See the case in Switzerland where in an outbreak at a hotel, all the people who only wore face shields got infected. No one who wore a mask, either on its own or with a shield did.

They're utterly ineffective, other than for protecting the eyes from splatter.

They do not stop exhalations (potentially containing virus) as they go straight round the edges

its already been clarified in scotland that if you wear a shield you also need a mask as they arent effective on their own

Because they don't work. Might as well be wearing a baseball cap and a pair of sunglasses for the supposed protection they give.