Audio problem: When the coach is driving through Portsmouth the pupils can be heard singing "a ticket to ride" but their mouths are all shut.
Factual error: On the coach when the camera is on Miss Booth you can see out the window a road sign saying 5 miles to Hatfield and 15 miles to Stevenage. Grange Hill school is set in North London and they are on their way to the Field Trip on the Isle of Wight via Portsmouth ferry terminal - the coach is heading the wrong way as both these towns are in Hertfordshire, which is north of London, and Portsmouth is on the south coast of England.
Suggested correction: Correct in theory, but in a large, densely populated urban area it would make sense to go towards the faster motorways which, depending on where in North London, would be the Northbound M1 and M25 (the latter goes round Greater London) than go completely in the right direction which would take longer as it means going 10 miles through urban areas and thus take a lot longer.
Continuity mistake: After Mr. McKenzie and the coach driver have loaded the coach boot Mac calls the driver Neil, but when they reach the ferry terminal the same coach driver's name is Tom.