Plot hole: When Danny Kendall first appears in series 9 (1986) he is in the third year, then the fourth year in series 10 (1987) but in series 11 (1988) he is put down a year to help him catch up with work he missed as he was in hospital for most of his fourth year. But in series 12 (1989) he is in the fifth year when he would be aged sixteen going on seventeen and he would not be legally obliged to stay on at school, as sixteen was the legal school leaving age then. When Danny died in series 12 the school planted a tree in his memory with a plaque in front of it giving his birth date as 8th January 1973 and death date as 22nd January 1989. His birth date should have been 8th January 1972, as he would have been seventeen years old when he died.
Continuity mistake: When Fiona and Calley are watching Ronnie on her new moped she does a right turn, passing a grey BMW waiting to turn right in the opposite direction. The angle changes and the BMW has disappeared as Ronnie rides over the same part of the road again. Also more parked cars have appeared on the road behind her.
Visible crew/equipment: When Ziggy and Trev enter the classroom there a shadow of the boom mike on the blackboard.
Continuity mistake: Ronnie arrives at school on her moped and parks next to a blue car that Vince is hiding behind - she removes her helmet, the camera cuts to Ziggy shouting at Vince, and when the camera cuts back to Vince, Ronnie takes her helmet off a second time.
Visible crew/equipment: Early in this episode, when the pupils are coming into school, Calley calls out to Vince "oi Vince, there's a lot of people looking for you" there is a reflection of a sound man holding a boom mike in the window of the blue car next to Vince.
Continuity mistake: During the memorial ceremony for Danny, Ronnie is reading a tribute but starts crying and is unable to finish it. Helen consoles Ronnie by embracing her, the angle changes to Ziggy and Robbie planting the tree and Ronnie and Helen have changed position - both are facing forwards, watching Robbie and Ziggy.
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.
Continuity mistake: While the end credits are rolling Mr McKenzie is taking a photo of Trev and Helen dancing. Behind them Gonch is dancing with Mandy. The angle changes and Gonch is now dancing with Calley.
Visible crew/equipment: In the scene where the students are setting up the American prom, a boom mike shadow can be seen on Calley's head when she, Ronnie and Fiona go over to talk to Helen and Georgina.
