Apologies if this has been shared previously, but if you're buying school shoes right now, I've just found Treads - they have a 12 month guarantee so if they become unusable in that time you send them back and they replace them at no cost, and they come with an insole to give your kid half a size extra when you take it out, so they won't grow out of them so quickly. Hope that's useful for someone!
I ordered and got a £5 off code for friends/family: TREE621084 - feel free to use it (which will give me £5 off my next order too), but you also get 10% off for signing up to the newsletter. I don't know if both can be used at the same time, so it's worth seeing which is the bigger discount depending on how many pairs you're buying. 
My referral link is here