A couple of points. Firstly, shelf stackers can social distance whilst doing their work. There is almost no chance that there can be effective social distancing in a classroom. Secondly, whilst I am sure teachers may be happy for shelf stackers to work, I suspect most would not demand that shelf stackers work against their will if they thought they were working in unsafe conditions.
Well they have been looking after kids of NHS staff and enabling them to work so they have certainly been contributing to lives being saved. I see where this is going - teachers have been part of the key workforce getting clapped every week for the valuable contribution they have made so far during this pandemic but any day now dim wits are going to start calling them traitors, egged on by The Mail.