Why isn't Naruto older than his friends?

Naruto has always been treated as the slowest in his class, but there's a curious detail that doesn't add up. Even after failing the Ninja Academy graduation exam three times, he's still younger than Sasuke, Sakura, and several other members of Team Konoha. How is this possible? Did he enter the academy before the others? Was he forced to take the exam multiple times without a real chance of passing? Or did Mizuki and even Iruka himself have some influence on this? Become a member to get incredible advantages:    / @konohachronicless