"The teacher eats from twelve to one."
The use of cong(从) and dao(到), is the "formula" you employ express from one time to another in mandarin.
从 + Time 1 + 到 + Time 2.
Hopefully this explanation is helpful to someone.
Actually, to speak more naturally we should remove 从 cóng from this sentence: 老师十二点到一点吃饭。
We usually add 从 for emphasizing the start of the action, and the sentence should be: 老师 从 十二点 吃 到 一点. (The teacher keeps eating from twelve to one.)
Its wrong to say "eats food" before saying "from 12 to 1" i guess. I find it (the order) a little confusing sometimes..