Oftentimes, the early parts of a long-running series won't quite match up with the later parts of that same series. Plot points will be forgotten, story elements will show up once and never again and characters will fade from relevance. This happens when the author wants to set up opportunities only to prioritize whatever's important to the story. These oversights may not mean too much in the grand scheme of things, but they can certainly irritate fans upon rewatching the work. A good example of this would be a plot hole that pops up fairly early on in the story of Naruto.
As one person on Quora points out, Naruto's early story seems to have a paradox. Naruto Uzumaki supposedly failed the Ninja Academy graduation exam three times before finally earning the title of genin. If this is the case, his peers should be much younger than him, yet they're all around his age. This seems like a big plot hole, but there may be ways to explain it. However, determining how Naruto could fail his graduation exam so many times and still end up with kids his age will require a deeper understanding of Naruto, as well as some minor speculation.
First, it's important to understand the setup. Prior to the start of the series, Naruto has taken the graduation exam two times and failed because he couldn't use the Clone Jutsu. At the start of the series, he is shown taking the exam a third time with students his age like Sasuke and Sakura. They all pass, but Naruto fails yet again. He's only able to "pass" shortly after he masters the far more advanced Shadow Clone technique and Iruka acknowledges him as genin material. This makes for a good standalone story about perseverance through humiliation, but when it's forced to connect with Naruto's overarching narrative, it creates contradictions like the one mentioned above.
In response to this Quora post, several theories have been put forth by commenters. One possible explanation could be that Naruto enrolled in the Ninja Academy before his friends did. If Naruto somehow got a head start on academy life a year or two ahead of his friends, that might explain how he's able to fail three times and still graduate with his peers. However, this theory would imply that Naruto is already familiar with the upperclassmen. If that were the case, he would have recognized Tenten, Neji or Rock Lee, but none of them recognize each other upon meeting up in the series proper. However, although this theory doesn't quite work, there are plenty more to choose from.
There's also the possibility that two of the exams Naruto failed were practice exams. If they were, he and all his friends could have taken them with varying results and still graduated at the same time as long as they passed the real exam. It's never confirmed in the series whether the other two exams were practice, so this theory could certainly hold water.
Another likely explanation would be that the graduation exam can be taken whenever the ninja-in-training wants. There have been cases in the story of Academy students graduating and becoming full-fledged genin at an early age; this happens to both Kakashi and Itachi. It's entirely possible that Naruto requested to take this exam early at least twice in order to get through academy life faster. It would line up with his eagerness to prove himself and become a great ninja someday.
This questionable plot point may never receive a formal explanation. Regardless, there are plenty of ways to justify it without breaking the established rules of the story. Until a concrete answer can be given by Masashi Kishimoto himself, fans are free to continue to come up with their own solutions and draw their own conclusions.
