父 fu dad 交 jiao exchange 爸 ba dad 校 xiao schoolhouse

父 fu4 dad
交 jiao1 exchange
爸 ba4 dad
校 jiao4/xiao4 proofread/schoolhouse

they are the same idea but sound differently. Originally a hand and an ax, 

https://hanziyuan.net/#%E7%88%B6

now two axes. It's easily remembered as looking like dad's moustache, or the idea of trading one ax for another.