If you are looking at selling at school events my advice would be small cheap items , no more than £10 each , I noted some of the prices at £75 , not really a impulse buy.
I've done quite a few craft fairs and even proper markets, and you can never tell what you'll make on the day. My best was over £1K in commissions etc, but only about £40 in actual on the day sales. Just for fun I took a £120 garden chair to a craft fair, and it was almost the only thing I sold!