Translation:The principal and the teachers work in the school.
I think that would be the place (-ejo) for the leader/boss (-estr-) of learning (lern-), since the order of the affixes matter greatly in Esperanto. In other words, this doesn't really make sense.
This might very well be true. I didn't think of that even though now it seems super obvious to me from my own description :D
That would presumably be lernejestrejo, rather than just lernestrejo, given that principal is lernejestro.
Work "at the school" is also perfectly correct English and a valid translation for this sentence.
Mi preferas por traduki "lernejestro" tiel "schoolmaster". Mi pensas ke tio ŝajnas simila ol la nomo de MtG karto. (Aŭ ĉu oni dirus "MlR karto" -- Magio: la Renkonto"?)
It is quite common, in the UK, to refer to the headmaster or headmistress as the head. That probably sounds weird to Americans.