Best way to kill a ton of people?

[Ideologue]

It's because we've been a bit soft in the lifetimes of everyone now alive that considers us an enemy.  Even Vietnam, while endlessly bloody, lacked easily understandable points of impact like Dresden or Hiroshima; you can have a Basra highway, but miles of twisted metal may be daunting, they are not frightening.  You can't blame them that they've forgotten the power of the air.

[CountDeMoney]

That said, I do think that you're right that targetting elementary schools would provoke the maximum emotional response.  But it might not be the response a terrorist would want--it would likely be anger rather than fear, I think.

I attended an event that Melissa Boyle Mahle was a speaker at a few years ago--retired CIA officer, wrote a really great memoir, one of the better ones about the agency in recent years--and she was asked what kind of attack she would be most concerned about in the post 9/11 years, and what would be the most impactful; she said it wasn't the low probability events of an WMD or 9/11-style hijackings, but three guys with AK-47s and grenades on three different school buses at the same time in three different places in America that would shut this entire nation down.  It's the most actionable, the most achievable, and the most debilitating.

[dps]

It's because we've been a bit soft in the lifetimes of everyone now alive that considers us an enemy.  Even Vietnam, while endlessly bloody, lacked easily understandable points of impact like Dresden or Hiroshima; you can have a Basra highway, but miles of twisted metal may be daunting, they are not frightening.  You can't blame them that they've forgotten the power of the air.

It's not just air power, either.  If the invasion of Iraq had been conducted the way WWII was, Baghdad and other cities would have been flattened by artillery fire before the infantry moved in.

[Siege]

That guy in Sarajevo in 1914 managed to kill 10 millions or so with one pistol shot.