"schoolboy error" meaning in English

{
  "forms": [
    {
      "form": "schoolboy errors",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "schoolboy error (plural schoolboy errors)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "British English",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Entries with translation boxes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with Finnish translations",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with French translations",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "A fundamental, simple mistake."
      ],
      "id": "en-schoolboy_error-en-noun-qnO7cSDq",
      "links": [
        [
          "fundamental",
          "fundamental"
        ],
        [
          "mistake",
          "mistake"
        ]
      ],
      "raw_glosses": [
        "(UK, informal) A fundamental, simple mistake."
      ],
      "synonyms": [
        {
          "word": "rookie mistake"
        }
      ],
      "tags": [
        "UK",
        "informal"
      ],
      "translations": [
        {
          "code": "fi",
          "lang": "Finnish",
          "sense": "simple mistake",
          "word": "aloittelijan virhe"
        },
        {
          "code": "fr",
          "lang": "French",
          "sense": "simple mistake",
          "tags": [
            "masculine"
          ],
          "word": "erreur du débutant"
        },
        {
          "code": "fr",
          "lang": "French",
          "sense": "simple mistake",
          "tags": [
            "masculine"
          ],
          "word": "erreur de débutant"
        }
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-schoolboy error.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/0/02/En-au-schoolboy_error.ogg/En-au-schoolboy_error.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/0/02/En-au-schoolboy_error.ogg"
    }
  ],
  "word": "schoolboy error"
}

{
  "forms": [
    {
      "form": "schoolboy errors",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "schoolboy error (plural schoolboy errors)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "British English",
        "English countable nouns",
        "English entries with incorrect language header",
        "English informal terms",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "Entries with translation boxes",
        "Pages with 1 entry",
        "Pages with entries",
        "Terms with Finnish translations",
        "Terms with French translations"
      ],
      "glosses": [
        "A fundamental, simple mistake."
      ],
      "links": [
        [
          "fundamental",
          "fundamental"
        ],
        [
          "mistake",
          "mistake"
        ]
      ],
      "raw_glosses": [
        "(UK, informal) A fundamental, simple mistake."
      ],
      "synonyms": [
        {
          "word": "rookie mistake"
        }
      ],
      "tags": [
        "UK",
        "informal"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-schoolboy error.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/0/02/En-au-schoolboy_error.ogg/En-au-schoolboy_error.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/0/02/En-au-schoolboy_error.ogg"
    }
  ],
  "translations": [
    {
      "code": "fi",
      "lang": "Finnish",
      "sense": "simple mistake",
      "word": "aloittelijan virhe"
    },
    {
      "code": "fr",
      "lang": "French",
      "sense": "simple mistake",
      "tags": [
        "masculine"
      ],
      "word": "erreur du débutant"
    },
    {
      "code": "fr",
      "lang": "French",
      "sense": "simple mistake",
      "tags": [
        "masculine"
      ],
      "word": "erreur de débutant"
    }
  ],
  "word": "schoolboy error"
}