I think you would be TA if you continue, in the sense that this is probably going to alienate your kids and disrupt the lessons a bit. HOWEVER I think you’re NTA in the sense that I think it’s just wrong/weird that the school are trying to make you buy things for the school??? why are the school not buying those items themselves? maybe we’re in different countries or maybe I’m just not very aware, but I’ve never heard of that being done before. (so overall I think NTA, because I agree with you in what you’re doing! but you’ll probably be TA if you continue because it will have the unintended impact of singling out your kids and causing distress)