Holden shares many details about Mr. Spencer, his history teacher, whom he visits at the teacher's home. Holden decides to vist Mr. Spencer because he liked as much as he could like any adult. All sorts of nose drops surround Mr. Spencer in his living room, and Holden deeply regrets having to see his teacher wearing a bathrobe or picking his nose for that matter. The worst comes when Holden feels "a lecture coming on," and Spencer inquires "What's the matter with you, boy? (Ch. 2).
Then Mr. Spencer pulls the ultimate dirty trick on Holden. He pulls out Holden's latest essay on the Egyptians and reads its aloud, right down to Holden's self-degrading note:
"I know this is junk, so it's OK if you flunk me, don't worry about it" (Ch. 2).
Holden feels that Spencer's lecture is condescending and full of cliches. He is disappointed that Spencer would stoop so low to embarrass him by reading his horrid essay, but ultimately concludes that Spencer must care about him to do so.
In Chapter 2, when Holden dropped by Mr. Spencer's apartment to say goodby, Spencer became stern and confrontational. He presented Holden with a History exam paper on which Holden had done poorly. Spencer read from the paper and challenged him over his poor performance, embarrassing him. Instead of a cordial goodbye or well-wishing, Spencer harangued him over an exam. Holden thought having his nose rubbed in the exam paper was a dirty trick because he'd politely stopped by to pay his respects before leaving the school.
Below is an example from the passage.
"I doubt very much if you opened your textbook even once the whole term. Did you? Tell the truth, boy."
...He started handling my exam paper like it was a turd or something. "We studied the Egyptians from November 4th to December 2nd," he said. "You shose to write about them for the optional essay question. Would you care to hear what you had to say?"
"No, sir, not very much," I said.
He read it anyway, though. You can't stop a teacher when they want to do something. They just do it.
The Egyptians were an ancient race of Caucasians residing on one of the northern section of Africa. The latter as we all know i sthe largest continent in the Eastern Hemisphere. ...
I had to sit there and listen to that crap. It certainly was a dirty trick.
...He stopped reading and put my paper down. I was beginning to sort of hate him.
...He put my goddam paper down then and looked at me like he'd just beaten hell out of me in ping-pong or something. I don't think I'll ever forgive hm for reading me that crap out loud.
It was a dirty trick for Spencer to take cheap shots at Holden when he was already depressed and discuraged from being expelled. It was a time when he needed understanding. Incompetent teachers like Spencer can cause kids to go suicidal, or, worse, postal.