Older boys school shoes, where can you get them cheap?

[lilibet]

Most places (asda, Tesco)go up to a 6 in shoes, but age 16 in clothes. What 16 year old boy takes a size 6?

My 12 year old is on 8's and it's not uncommon. Is there anywhere that I can get cheap school shoes for this size?

clarks kids shoes go up to a 10!
not cheap... but they will last longer!