I hope you don't mind me putting my ha'penny in but this is a bit of a bugbear of mine
Are you talking about the school bus or one of the 'timetabled' Stagecoach buses? It's just my DS started KES in September and we have been having such 'fun' with the No.16, it seems to have a timetable all of it's own
(I've just read this bit back to myself, think I wrote this too late at night!!) .
If you're talking about the No.16 then DS can get home anytime between 16.45 and 17.45, dependent on whether it's full and he's had to get the slower No.18 & G1 via Warwick bus station, or if the 16 is simply late. Generally speaking the 16 seems to leave Stratford (Bridge St) about 15-20 minutes late (it's supposed to leave at 16.17) and takes about half an hour to get to the north end of Warwick.
You sort of get used to it after a while but it doesn't leave much time to eat and/or do homework/ other activities. That said DS has done brilliantly finding his way around the buses and finding alternatives.
Hope this helps.