you are a mean professor... but "es" would be "eres" instead.
Ella es una chica mala
You are a bad teacher/professor. (female) Unless you are being intentionally disrespectful, you normally wouls not address a teacher or professor in the tu form.
Is your mathmetics professor a man or a woman.
who is the professor
La profesora es... *and you insert her name here*
es una clase de matematicas means is a kind of mathematics
Mi profesora de espanol es Senora... then you would put the name.ms Esparza
It means "it is one" referring to a feminine noun, e.g. es una mujer = it's a woman.
Yuh Mean como todas oh una exactamente, si son todas es la mala oh el inisente amigo
mi amiga es mala
It means: Is the one.
A very nice girl.