the school needs help to teach music.这一句既然help已经是动词了.为什么要加to.

help在此为名词晓得，我只是想问你，为什么要加to。我理解的是，to teach music 是目的状语teach music不是状语的嘛，为什么要加to。还有，we need you to help with sports for English-speaking students.能不能把其中的to改为at?for？with？to teach music 是目的状语，加上TO表目的啊，就像例句中的 TO CLEAN THE AIR, i planted flowrs to clean the air,