At 15 years old, Peter Parker really lowered the age limit to being an Avenger when he made his Team Iron Man debut in Captain America: Civil War. That said, his status as one of Earth's mightiest heroes is still up in the air in Spider-Man: Homecoming. It's unclear if Spider-Man is an Avenger after just one fight against no discernible evil, as fans who have seen The Avengers know that becoming one of the most elite superheroes in the world is a bit more complicated than that.
In Spider-Man: Homecoming, Peter Parker desperately wants to be an Avenger. When he's stuck in class, he watches videos of Spider-Man on Youtube and relives his exciting day fighting against Ant-Man and Captain America. And after school, he ditches homework in favor of fighting local crime in New York City.
But, despite his passionate work ethic, Spider-Man is not really an Avenger — not yet. In fact, the young web-slinger spends the entire film trying to convince to Tony Stark that he has what it takes to join the Avengers for good. His most precious wish is to move into the Avengers compound upstate, where Cap used to train Vision, Wanda, and Sam. But, in a rare show of wisdom and restraint, Tony doesn't give in to Peter's desires. Instead, he keeps his new protégé in NYC, away from the big super-villains and government involvement. And he's right. Peter Parker shouldn't be an Avenger, and there are a few big reasons why.
He's Basically A Child
Say it with me: Peter Parker is a minor. Technically, Tony's "recruitment" of Spidey in Civil War could be considered a kidnapping. I doubt Aunt May would be OK with her nephew dropping out of high school to become an Avenger, and something tells me she would not be afraid to press charges should Tony ever take Peter on another international trip without informing her.
He Doesn't Have A High School Diploma
Peter has just begun his second year of high school in Homecoming, so leaving to join the Avengers would be a pretty dumb move. After all, one can't expect to be a superhero forever. When he's older, with a bad back and busted knees, he might need a career to fall back on, which means he should probably get a high school diploma. On a practical level, it just doesn't make sense.
The Sokovia Accords
If Spider-Man was to join the Avengers right now, that means he'd have to decide to sign the Sokovia Accords and pledge to only jump into battle with government permission. At the end of Civil War, Tony seemed to understand the pros and cons of the Accords, but he still operates within them, as does everyone at the Avengers compound. Putting that big of a decision in the hands of a teen with superpowers could cause him to make a huge mistake and put him and his aunt in danger. For now, it's better for everyone if Peter stays under the radar.
He Doesn't Understand His Powers
Peter hasn't been trained in combat. He doesn't know how to fight and hasn't really tested the extent of his powers yet. To throw him in with the Avengers would be foolish, especially considering the fact that both Black Widow and Captain America, the two who were training the new recruits, seemed to have cut ties with the Avengers compound at the end of Civil War. Which brings me to my final point...
Tony Stark Is A Horrible Mentor
Look, I know Tony is brilliant and all, but he really doesn't know anything about training superheroes. He loves to take unnecessary risks without thinking and, despite bringing Spidey into the fold, he shows no desire to teach Peter himself. In Homecoming, he pretty much just throws Spider-Man into the deep end and waits to see if he sinks or swims. With Tony as his only mentor in the Avengers, Peter would be missing out on all Cap and Black Widow have to offer — namely combat skills, team building, and actual training. It's really best for Peter to wait to join the Avengers until the Avengers are actually back together again.
Peter Parker isn't an Avenger in Spider-Man: Homecoming, and it's really for the best. However, fans can expect him to fight alongside the Avengers once again in Avengers: Infinity War. Hopefully this time he'll be fighting with all of the superheroes, not against some of them.