Ok, that's a bit of an exaggeration. Bible class didn't make me an atheist, but it certainly contributed. Here's how.
I attended public school for grades K - 12, but before that I spent a brief year or so of pre-K education at a Catholic parochial school, where daily Bible class was part of the curriculum. In this class we were taught stories from the Bible as historical facts, but in me this backfired and had the opposite effect.
This was achieved via the story of Samson and Delilah. The basic gist is that Samson, an Israelite hero with incredible strength (the source of which is his long hair) falls in love with a Philistine woman, Delilah, who seduces Samson into revealing the secret of his power. After which, Delilah has Samson's hair cut in his sleep, thus robbing him of his power, and then blinds him and puts him to work doing forced labor. Eventually, Samson's hair grows back and his strength returns, and at a festival where Samson is being shown off as a prize captive he snaps his bonds and pulls down the pillars of the temple resulting in the death of himself and 3,000 Philistines.
Despite the presentation of this tale as objective fact, my young mind could not help but immediately recognize Samson for what he was - a superhero. At this time I was an avid reader of comic books, and Samson's super human abilities sounded to me not much different than the powers of Superman, The Incredible Hulk, or Thor the God of Thunder (who perhaps doubly makes the point existing as both a Norse God and Marvel character.) And if these stories were obviously fiction, was not the story of Samson also probably fiction?
This was not enough to drive me to full blown atheism, as I would remain an agnostic/deist for some years yet, but it was enough to make me seriously doubt the historical veracity of the Bible, especially in regards to claims of the supernatural.