Episode #1.3 - S1-E3
Factual error: As Trisha and Judy leave the class, Mr Mitchell says "see you tomorrow." After which, Trisha asks Judy, "Did you see Top of the Pops last night?" Top of the Pops was shown on a Thursday night when this episode was shown in 1978, making this day Friday - there is no school on Saturdays.
Factual error: One of the rockers taking part in the musical is wearing an Iron Maiden T-shirt, this musical is set in 1962 and Iron Maiden weren't formed until 1975.
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.
Factual error: Shannon asks Leah if she knows what happened to Tom Smith - she replies that Tom has gone to university, but in the previous series Tom was only in his first year of sixth form, and it takes at least two years in the sixth form to study for the A levels required for a university place.
Suggested correction: Although normally A-levels are taken after 2 years, it is possible (and often done) to study them in one year.
Factual error: Justine and Maria are in Justine's bedroom. Justine is showing Maria the photos on her bedroom wall of her family and school friends. There is a photo of Banksie and Zammo on the wall. These two boys left Grange Hill at the end of series 10. Justine started in series 11, so she would not have known them.