Hi Ian,
I used to do an annual clean at a local infants/junior school until the governors persuaded the headmistress that the money would be better spent on books.
Remembering the amount of play-dough, chewing gum, vomit, urine etc., in addition to general soiling that I used to remove every 12 months, I can only imagine what the carpets are like after 6 years of not being cleaned.