In the Fantastic Beasts franchise, Newt Scamander has been the story's focal point as his adventures as a Magizoologist, but his life took an unexpected turn as he was pulled into a harrowing secret war between Dumbledore's forces and the nefarious radicals that made up Grindelwald's army; however, Newt's complicated personal life didn't begin in his adult life. Instead, it started far earlier with events that led to his expulsion from Hogwarts School of Witchcraft and Wizardry, but the circumstances behind his expulsion weren't as cut and dry as they would seem.
One of the biggest constants in Newt's life has been his love of magical creatures. Unfortunately, this adoration for the animals that couldn't speak for themselves has gotten him into messy situations even before he found his way to New York City. While his story was never expertly shown, there have been explanations regarding him carrying a magical beast that endangered the lives of the students at Hogwarts, but the question for many fans of the films of what animal he had was never explored, but The Case of Beasts: Explore the Film Wizardry of Fantastic Beasts and Where to Find Them offered some answers to these burning questions.
According to the text, Newt was expelled due to his possession of a Jarvey, which was both illegal to own and a violation of Animal Welfare Laws 101/304. In the Wizarding World, the Jarvey was a ferret-looking creature capable of human speech. However, the words that it would use were often rude or vulgar and continued for long periods. In addition, while his diet never included a taste for humans, its methods were often more violent than others when hunting its prey. In short, these creatures are very abrasive but otherwise harmless to humans. As a result, Newt's expulsion was never cleared, thanks to the intervention of Dumbledore, who probably saw that newt was caring for it for noble reasons, and the creature itself was a far cry from a dragon.
While the Jarvey was likely still a huge factor in Newt's expulsion, The Fantastic Beasts and Where to Find Them: Magical Movie Handbook revealed that there may have been more to his disciplining. Leta Lestrange was a childhood friend of Newt and carried her own demons even at a young age. However, she never let it deter her from her friend or interest in magical experiments. It was later revealed that one of her experiments involved Newt's Jarvey, which put another student's life at risk. Rather than giving her a chance to fess up, Newt took the fall for her.
While Newt's expulsion was on record, it was also never cleared, as he was shown with his wand intact. In Hogwarts, expulsion often included a wizard or witch's wand being snapped in two, like what happened with Hagrid's. There's no denying that this was due to Dumbledore's interjection, but what made Newt's strange case so impactful was the instructor's foresight regarding the young wizard.
Dumbledore likely saw Newt's kindness, selflessness and heroism and knew it could and should be used for a greater purpose. His love of animals was invaluable in a world where Magizoology didn't exist, and to stamp out that dream would've been a disservice, but even more powerful was his willingness to care for an illegal creature out of kindness and to take the fall for something he obviously didn't do. Albus saw his moral compass clearer than most and knew that he would make a difference. Thankfully, his decision proved correct, as Newt has become Dumbledore's moral center on more than one occasion.