The jiāo reading is the everyday verb: 教 + object - 教中文 (teach Chinese), 教书 (teach as a profession), 教课 (teach class). When 教 takes a direct object describing what is taught, it stays jiāo.
mistakes
教 has a sister reading 教 used in most compounds - 教育, 教师, 宗教. The active verb "to teach (someone something)" is jiāo; the bound morpheme inside fixed compounds is jiào.
Right strike radical - the indexing radical. Pictures a hand holding a stick. In ancient pedagogy, teaching meant disciplining: the master tapped the pupil with a switch to enforce the lesson. Same radical anchors many command/correct verbs: 改 (alter), 政 (govern), 敬 (respect), 散 (scatter).
Left component - pictures an elder (耂) above a child (子), the canonical filial-piety image. The original sense of 教 was "to instil filial duty", so this side carries the moral weight: values passing from elder to younger.
