Gryffindor (Im)Morality: The Education of Miss Granger
We first meet Hermione on the Hogwarts Express.

The Grangers, middle class dentists, apparently raised their daughter to play by middle-class values: to be hard-working, law-abiding, conscientious, and helpful. The Hermione we first met clearly expected that doing her best and playing by the rules would be rewarded.

By adults, most probably, but at least not punished by other children.

I grew up in an anti-intellectual mill town, and I had learned by second grade that being "too smart" was socially iffy. I was still, like Hermione, naturally competitive, a perfectionist and a teacher-pleaser, but I tried desperately to hide this from other children. When my family moved out of town and I did go to a new school, I started off by concealing my GPA and refusing to volunteer in class.

Hermione did the exact opposite. She apparently expected to be valued for her intelligence, talent, drive, and rule-upholding. So her previous social experiences must have reinforced that it was okay to be both a good girl and a good student.

(Notice that Hogwarts changed that completely: when a Ravenclaw commented, 5th year, that her Protean Charm was NEWTS level, Hermione brushed it off. As I would’ve, having repeatedly experienced being punished for doing well. But Hermione was innocent of that reaction as a Muggle-born firstie.)

Unfortunately Hermione believed in what she had read, and she insisted that the Sorting Hat put her in the "best" house, Gryffindor, rather than in Ravenclaw where her talent, intelligence, and diligence would have earned her respect, companionship, and certainly a healthy dose of competition.

Her first two months in her new House, she tried repeatedly to get her new housemates to obey the rules and to win admiration by gaining House points for her academic performance. Her reward was to be labeled "a nightmare" and become a total social outcast.

But Hermione was bright, and she learned. What she learned was that to get friends in her House, she had to abandon the principles with which she was raised. And Gryffindor was the best House, so it was right to adjust to its norms.

Look again at the troll incident, at the lie Hermione told the professors. It's presented, from Harry's POV, as Hermione lying to save the boys from being punished—which loyalty they rewarded by including her in their friendship. But in fact Hermione did not need to lie to save the boys from McGonagall's wrath—the truth would have served as well or better for that. Let’s look at the scene.

Then a small voice came out of the shadows.

“Please, Professor McGonagall—they were looking for me.”

“Miss Granger!”
…
“If they hadn’t found me, I’d be dead now. Harry stuck his wand up its nose and Ron knocked it out with its own club. They didn’t have time to come and fetch anyone. It was about to finish me off when they arrived.”

Note that all of the above is factually correct (although Hermione had no way to know the boys had come to the corridor to warn her, she certainly knew that they ran in when they heard her scream). Would that not have been sufficient to get the boys their ten points?

So what was the point of the omitted statement, the lie? Well, let’s look at it.
“I went looking for the troll because I—I thought I could deal with it on my own—you know, because I’ve read all about them.”

Ron dropped his wand. Hermione Granger, telling a downright lie to a teacher?
…

“Miss Granger, you foolish girl, how could you think of tackling a mountain troll on your own?”

Hermione hung her head. Harry was speechless. Hermione was the last person to do anything against the rules, and here she was, pretending she had, to get them out of trouble. It was as if Snape had started handing out sweets.

“Miss Granger, five points will be taken from Gryffindor for this.”

The actual point of Hermione’s lie was that it was gratuitous.

Hermione the goody-good publicly denigrated her own abilities and demonstrated, by doing it, that she was willing to break rules (lying to teachers must surely have been the worst of sins in her book) to be accepted by her peers. And it worked. She sacrificed her principles; she gained conditional acceptance.

Acceptance, of course, was conditional on her continuing to sacrifice her parents’ principles. In her subsequent Hogwarts career she smuggled a dangerous creature into the school to conceal a crime; she twice assaulted a teacher; she stole; she brewed an illegal potion; she consistently cheated in classes by doing friends' homework or (potions) classwork for them; she lied whenever required. She became, if you want to get technical, both an accomplice to crimes and a criminal herself. But none of it was to benefit herself, so it was all okay.

As she explained, loyalty and bravery matter more than book-learning and cleverness. Or morality.

When she was made prefect, like Lupin before her she sat by and allowed her personal friends to get away with flagrant infractions of the rules, infractions that harmed other students. She allowed Ron to abuse his position (confiscating a Fanged Frisbee to play with it himself) and Harry to attack people for his idle entertainment. She hexed other children herself: cheating Ron's way onto the Quidditch team, and (apparently permanently) disfiguring Marietta for "sneaking" and turning in the illegal DA (which hadn't been illegal when Marietta had signed that parchment: Marietta had never signed up to defy the Ministry, only to hang out with her best friend and get some extra lessons in DADA).

She had learned the lesson of Gryffindor: there are no moral standards. Absolutely any behavior is acceptable if done to help a friend.

The girl who performed Unforgivable Curses in Book Seven without compunction or remorse is already there in Book One. Lying to her teachers to buy friendship.

Doing evil for the sake of your friends demonstrates the depth of your loyalty to them and is therefore Good. Thus saith the Gospel of the Gryffindor.

Thanks be to Godric.