Having tried for about 40 years to buy as ethically as possible, I would say these are recurring dilemmas, with no correct answer. The Ethical Consumer website is very useful and you can look at different criteria. I would praise her thoughtfulness, suggest she makes her own decision ( I'm sure you did!) and say that you respect her reasons and would like her to respect yours. That is how our family rubs along! And how lovely to have such a thoughtful granddaughter and thoughtful school as well.
Disappearing contributors - part 2
It's official: Grandparents are good for children
My father 81 needs wrist surgery for a bad fracture and I am worried

