In the beginning, as is usual with beginnings, everything worked out.
Loki Laufeyson and Tony Stark hung out with the same crowd—intelligent kids, the ones who wanted to major in physics or astronomy or both in college; not popular exactly, but smart and witty enough to earn respect from everyone else in the school. When they started dating, no one was surprised—they had the fastest brains out of their crowd, and their constant banter could have been considered flirting—not that anyone would have ever said it to either Loki or Tony's face until after they announced they were a couple. And it was nice to see them finally happy, nice to see Tony loop his arm around Loki's waist when they walked down the hallways together, nice to see them sitting as close as is physically possible in the library, their legs twined under the table, Loki's long dark hair splayed out over Tony's shoulder as the older teen carded his fingers through its greasy, soft strands. When they went to Starbucks after school with the group for a drink, Loki would always order for both himself and Tony, who would then pay for their drinks and any pastries they may have gotten.
They fought, of course, because they were Tony and Loki, and they were going to fight whether they were best friends or fucking each other's brains out, but usually by the end of the week whatever it was had resolved itself, and one of their group—usually Steve, the history buff who was so innocent it could have been labeled adorable—would walk in on them in a deserted classroom, heavily making out, one of them bent backwards over a desk while the other worked quickly at his belt buckle.
So in the beginning, it was good. Tony and Loki—an entity unto themselves, a couple so well-known throughout the school that the students did not say one name without immediately adding the other—were happy together, and if, as their junior year melted into summer and then into senior year, their group started noticing that the fights were getting more and more vicious and there was often very nearly visible tension between them during study sessions or at Starbucks after school, none of them said anything. Loki continued to give Tony back massages at football games and read Shakespeare to him in the back of the library when they thought no one was listening. Tony continued putting bags of candy in Loki's locker and wearing his green button-down shirts to school on Mondays, letting the world know who he'd spent the weekend with. (As if Steve and the others didn't hear enough about it from Thor, who complained that his brother and Tony were too loud at night but that Tony was good enough competition at Call of Duty to be forgiven.) The fighting, that was nothing. Just hormones. It would pass.
But then the Christmas dance happened, and everything got shot to hell. The perfect beginning, which had fallen into a slightly damaged middle, came to an abrupt and shattered ending which left everyone shocked and confused—although Natasha, when pressed, would admit she was not entirely surprised.
No one knew exactly what had happened at the dance, only that it had involved a very drunk Tony Stark suddenly appearing half naked from behind the bleachers, while a red-faced Loki Laufeyson screamed obscenities at him—and the girl he was with. Tony put his hand on Loki's shoulder, Loki shrugged it off, called the girl a slut, then hit Tony as hard as he could across the face. They threw punches until the principal stepped in, separating them, forcing them outside. The group knew better than to follow—not even when neither of them came back in the gym for the rest of the night—but by the following Monday, it was official: Tony and Loki were no longer together; they weren't even speaking. Loki separated himself gradually from the group, despite Thor's protests—by the time they graduated in June, Loki was an outsider, and Tony had made all the appearances of moving on.
They all ended up going to the same college—Tony and Bruce majored in physics, Steve in history, Thor in Greek mythology, Clint and Natasha in astronomy, and Loki in linguistics and literature. Although they were not on speaking terms with him anymore, they tried being civil to him in passing—except Tony, of course, because he had Pepper now, and he'd brutally murder anyone who even suggested that he occasionally looked at Loki with an expression in his eyes of such desperate longing that he appeared to be crying.
Freshman year passed by silently and swiftly and with a ghost of heartbreak on its shoulder. And then sophomore year started, and everything changed. Again.