我來試着回答一下吧。
毫無疑問teaches當然不是介詞,它只是一個動詞的第三人稱單數,在句中常常作謂語,其後面常跟teach sb sth.或者teach sb to do sth.例如:Miss Li teaches us English.
Mt father often teaches me to learn to swim
希望我的回答能夠儘快幫到你啊!