"blackboard jungle" meaning in English

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  "lang_code": "en",
  "pos": "noun",
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          "ref": "2011, William J. Reese, America's Public Schools, page 309:",
          "text": "[…] blackboard jungles abounded in the media, the widening gap between suburban and urban school performance was frequently in the news.",
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          "ref": "2015, Martha Stephens, Me and the Grandmas of Baghdad, page 64:",
          "text": "[…] could subdue any renegade person or family, but I wonder if they would not meet their match in the blackboard jungles of today.",
          "type": "quote"
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      "glosses": [
        "A school with dangerous, unruly pupils."
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      "id": "en-blackboard_jungle-en-noun-dFxE150k",
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      "related": [
        {
          "word": "Blackboard Jungle (1955 film)"
        }
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    }
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  "word": "blackboard jungle"
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  "pos": "noun",
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      "word": "Blackboard Jungle (1955 film)"
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  "word": "blackboard jungle"
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