There's a switchblade in one hand and a civics textbook in the other here, and the film spends most of its runtime deciding which one it's actually going to use. Richard Dadier, unfortunately, keeps reaching for the textbook. The trouble isn't Glenn Ford — he does what he can with the role — it's Dadier himself, a man who sees every problem in flat, noble terms: spot the issue, deliver the lecture, restore order. Which is admirable enough, but it doesn't make for gripping drama.
What saves it is Sidney Poitier. As Gregory Miller, he's got the charm and the edge that Dadier can only dream about, and the film wakes up the moment he's given room to breathe.
I wish the script trusted that relationship more, because everything else feels bolted on. The women barely register as people, the baby-in-peril subplot exists purely to manufacture stakes, and the teenage slang sounds reverse-engineered by committee.
Poitier would later end up in the softer cousin of this with To Sir, with Love, swapping New York for the East End and losing most of the grit along the way. Whatever Blackboard Jungle gets wrong, at least it isn't that soft.
It clearly thought it was staring into the abyss. Turns out it was mostly chalk dust — though whenever Poitier is on screen, something briefly catches fire.