Florida school district leaders are faced with a school security dilemma. Lawmakers are requiring them to add armed safety officers or “guardians” to every elementary, middle and high school campus, and they set aside $170 million for the task. But that won’t come close to projected costs. The gap — as little as $500,000 in some counties, more than $10 million in others — is leading to some potentially unpleasant choices. That’s because school board members also face other budget demands, such as a state-mandated increase in employee retirement contributions, paired with a tiny rise in revenue for general operations, if not a decrease. They’re also required to maintain a 3 percent reserve account, or be hit with new and tougher penalties the Legislature imposed in its recent session.