Ok. So for those who are scoffing at teaching being a higher viral load job, you need to firstly have a memory (as the government have backtracked and whitewashed over lots of data and articles linked to this when they wanted to reopen schools) and ensure that you have all facts to hand.
In the link I'm going to add in, it clearly states that the primary school teaching staff exposure is around 50 with, clearly, medical workers such as nurses having a far higher exposure rate of 80/90. So from that information one could say that teachers need not worry.
But when you then look at the rest of the data and notice that other professions/jobs that have far far less viral exposure are being 'allowed' to wear masks (and in most cases, being expected to) you can then see how disgusting and questionable it is that teachers have up until this point effectively been banned from wearing a mask.
https://www.ons.gov.uk/visualisations/dvc806/occupationsexposureetodiseaseedata.xls
For any primary teacher in here, you have the right to wear one. The unions state that we have the right too and this is backed further by the HSE that states that all employers should support an individual employees decision to wear a mask. This overrides any DFE advice as this is employment rights and all you have to do is put it in writing to your Head that you will be wearing a mask. Any Head that puts in writing back stating that you can't is on very very tricky legal ground as, if you then go on to catch COVID-19 at work this would be their fault as they did not allow you protection.