Oh i never even noticed that page before. They keep it very hidden. If you click on "routes" then "bus routes" it just redirects to the TFL website. You have to click on "events and hire" then "school routes" to find it.The school routes also have a route map on their website, but unusually, they also include notes for drivers, such as 'risk of grounding'. See attached for an example.
School routes - Go Ahead London
Surrey School Routes Go-Ahead London will continue operating Surrey School routes 618, 668 & 669 Route 615 will transfer and be operated by Falcon Bus, for their website and route information please Click Here Route 619 will transfer and be operated by Metrobus, for their website and route...
So it seems that they do indeed publish their faretables for the 618 and 668 and 669 online if you know where to look. Not quite as hidden as i thought. It appears that £6.00 Single or £10.00 Return is a flat fare no matter how far you travel. They also have £40.00 Weekly or £136.00 Monthly which seems crazy for just one bus a day in each direction on school days only. You can get weekly and monthly tickets for less than that covering an entire bus company across multiple counties. They definitely seem to want to discourage ordinary passengers.
Interestingly it seems that Go Ahead London also used to run the 615 and 619 in the area. The 615 transferred to Falcon Buses recently. The 619 transferred to their sister company Metrobus Crawley recently. I think this was only in the last few years that Go Ahead London stopped operating them.
I also have a vague memory of Go Ahead London operating the 318 service (Epsom - Tattenham Corner - Banstead) and the 516 service (Dorking - Betchworth - Box Hill - Headley - Leatherhead - Ashtead - Epsom) at one point in the mid 2000s i think. They have switched bus operators so many times (eg, Buses Excetera, Countryliner, Epsom Buses, Sunray Travel, Surrey Connect, etc) but there was definitely a period of Go Ahead London operating them. These were ordinary day bus routes rather than school routes.