https://dictionary.cambridge.org/zhs/%E8%AF%8D%E5%85%B8/%E6%B1%89%E8%AF%AD-%E7%AE%80%E4%BD%93-%E8%8B%B1%E8%AF%AD/%E5%B0%8F%E5%AD%A6%E7%94%9F
小学生的常识 ... used before you mention a fact that is familiar to everyone, including children: As every schoolboy knows, the earth revolves around the sun.