Potter is pleased to be receiving from the council a new assistant. However his pleasure evaporates when he discovers that the new assistant is a black man - Sidney Noakes. Potter's discomfort intensifies even further when it becomes apparent that Sidney is much more efficient and proficient at the job - his mission now is to get him out.
In the 1970s there were very few black characters on TV and when they did appear it was almost always in stories where their race was an issue and that is certainly the case here. In comedy the handling of ethnicity was commonly very heavy-handed and that is regrettably demonstrated in this episode. It must be borne in mind though that for its time this would not have seemed controversial. These were very different times and while racism remains a problem in Britain today it was much worse and often openly tolerated back then. In some respects this episode did try to strike a progressive tone for its era and it needs to be judged in the context it was made.
For example it's significant that the prejudice was largely focused on the character of Potter, the most flawed and least sympathetic figure in the show. The other staff simply regard Sidney as another equal member of staff and appreciate his competence and work ethic set against Potter's incompetence and inefficiency. However some of the pupils do feed Potter's prejudice and gullibility by telling him that Sidney is a black power radical although typically he garbles their information. It might be argued they were trying to expose the foolishness of Potter rather than being prejudiced themselves but the end result was still to make him more determined to get Sidney out.
The show had actually addressed racism in a much earlier episode - "Panalal Passes By" from Series 2. In that instance the prejudice was focused on narrow-minded parents while staff and pupils were fully behind the diligent and intelligent pupil Panalal and his committed parents. While that episode still had some flaws it was rather better than this one, perhaps due to it being penned by original writers Esmonde and Larbey and being produced when the show was fresher. Perhaps in different circumstances this would have been more sensitively done and more successful as a result. Derek Griffiths as Sidney is an impressive actor and does a typically good job but he was not helped by the material here.
It must be said that there is effective humour on screen at the rightful expense of Potter's racism but we also know that there would be plenty of racist viewers - certainly in that era - who would have felt only too comfortable with his views. This was often the dilemma of such comedy back then - were viewers laughing at the stupidity of racism or more disturbingly laughing with it?
It's worth noting that Potter possibly having an assistant had been raised before early in Series 3 when Dennis Dunstable - who was struggling to find a job - had been suggested as a candidate and once again Potter displayed his narrow-mindedness, in that instance because of Dennis's learning difficulties. No doubt Dennis would also have been better at the job than Potter - as indeed would be almost any assistant. Maybe it would have been better to have written the story of a new assistant upstaging and embarrassing Potter without the issue of ethnicity being involved and there would still have been plenty of good humour in that scenario..
There is a small sub-plot in which Ffitchett-Brown tries to get permission to teach some sex education to his class with the out-of-touch, prudish Head trying to block him. Again this theme had been covered in a much earlier episode which may have been why it was not fully explored here. Interestingly the generally traditional Miss Ewell is more approving of Ffitchett-Brown's ideas and this shows that she was generally a much more perceptive and open-minded teacher than the Head. The fact though that this story wasn't opened-up maybe also indicates that this new - and promising - teacher wasn't being fully utilised on screen. Deryck Guyler as Potter now had first billing on the credits so perhaps it wasn't surprising to see him take centre stage but it did seem a missed opportunity.
Finally the pupils are again barely featured in this episode and as mentioned earlier their contribution is largely to fuel Potter's prejudices. While the staff were generally doing a sterling job sustaining the comedy the pupils at this stage had become a pale shadow of those of the first three series.