The most powerful was probably the end of Gets a Little Stranger. Wendy reveals her third ear, but Louis assures her that he still loves her. While saying this, he gives her a look that makes her feel confident that he means it.
Then there was the event that led up to this moment: Wendy Nogard is set to cross the Moral Event Horizon by "accidentally" dropping Mrs. Jewls' new baby out of the thirtieth story window, but on her way, being a mind reader, she hears the baby's thoughts of pure love and trust and undergoes a powerful Heel–Face Turn.
The end of the "Love and a Dead Rat" chapter in Falling Down, in which Dameon, whose crush on Mrs. Jewls was no secret, overcomes his teasing classmates and confesses his love to Mrs. Jewls despite knowing there is a Mr. Jewls. Mrs. Jewls tells Dameon she loves him too and it's okay even though she is married.
"Just because I love Mister Jewls, it doesn't mean I can't also love you. Love is different from most things." She picked up a piece of chalk. "If I gave my piece of chalk to someone, then I wouldn't have it anymore. But when I give my love to someone, I end up with more love than I started with. The more love you give away, the more you have left."
Benjamin Nushmutt spends most of the second book thinking that the other students only like him because they think his name is Mark Miller and worried that they'll turn on him when they learn the truth. When he finally does reveal his real name, they don't care and accept him wholeheartedly.
In the third book, Mrs. Zarves has a breakdown after a lifetime of no one ever noticing her existence finally gets to her. She tearfully leaves Wayside School, only to be stopped by the mysterious men in business suits who show up in each of the books. They assure her that she matters, and that her students still need her.
The men in business suits are good at this. The chapter "Freedom" has Myron, who's always had a bit of a nervous problem, melt down when he compares his own stuck-in life to that of a bird outside his classroom window. As he sulks, the men arrive and offer him a choice: he can be safe, with all the little compromises and responsibility that comes with it... or he can be free. He thinks about it, and then chooses to be free. And nobody ever bothers him again.
He didn't work on the test. Instead, he pushed it aside and sat on the floor.
And there was nothing they could do about it.
He was free.
After Maurecia reports finding $20,655 on the playground, the elderly man who lost it moved Maurecia to tears with his story about how he made the money making pencils by the penny for fifty years and feared that he would have to make more. Then the elderly man announces his intentions to open an ice cream parlor with the money and for her honesty, Maurecia is rewarded with $500 and a lifetime of free ice cream, her favorite thing in the world.
Ms. Nogard reading the baby's "thoughts". Thoughts is in quotes because the story says that babies don't think in words; they think in pure love and trust. It causes the teacher to have a Heel–Face Turn then and there.
Her Freudian Excuse is sad enough. Her ex-boyfriend? The one who's knee-jerk reaction to the third ear led to Wendy Nosgard's Face–Heel Turn? He died alone, always feeling like something was missing. Points to Louis for providing a good example of Second Love for kids.
Just try to hold back Tears of Joy when the Scotsman who lost his voice to Mr. Gorf finally gets it back, and greets his wife for the first time in 20 years.