What is the summary of Chapter 19 of To Sir With Love?

Mr. Braithwaite is getting to know his students better. He sometimes visits the small shops of Watney Street where many of their parents work, and so is better able to understand their lives.

A new teacher, Mr. Bell, arrives at the school, and is in charge of P.T. class for some of the senior boys. Mr. Bell is impatient and often unkind, berating the boys frequently and telling them they "stink like old garbage." As a result of complaints, Mr. Bell is reprimanded by the headmaster, and emerges more bitter than ever.

In class, Mr. Bell is particularly hard on Buckley, who is heavy and poorly coordinated. One day, he forces Buckley to attempt a difficult jump on the vault, despite the boy's hesitance and the protests of his peers. Buckley crashes clumsily into the apparatus, breaking it, and as he lies on the ground and his friends gather around to help him, Potter explodes in rage, picking up the broken part of the vault as a weapon and going after Mr. Bell. Tich Jackson runs for Mr. Braithwaite, who comes quickly and defuses the situation. Mr. Bell leaves, and the boys express their fury that he should have so cruelly made Buckley perform a maneuver so obviously beyond his capabilities. Fortunately, Buckley, though shaken, is all right.

Back in their regular classroom, Mr. Braithwaite tells Potter that he was out of line in attacking his teacher as he did. Potter and the boys are outraged, as it is clear that Mr. Bell's behavior was untenable. Mr. Braithwaite agrees, but stresses that ultimately, it is their own behavior for which they are responsible, and that, in life, it is of utmost importance that they learn self-control in even the most infuriating situations. Potter admits that he is not "quite pleased and satisfied" with what he did, but the boys persist, telling Mr. Braithwaite that he does not know what it is like to be "pushed around." Their accusation strikes a chord with their teacher, who has been "pushed around" all his life because of his race, and he tells them that it is easy to resort to violence when wronged, but so much harder to "be a bit bigger than the people who hurt (you)." Recognizing his sincerity, the boys are subdued, and Mr. Braithwaite challenges Potter to do the difficult thing and apologize to Mr. Bell, for his own sake. Potter goes to do this immediately, accompanied by Denham and Seales, and they return with Mr. Bell, who offers an uncomfortable apology of his own (Chapter 19).