Learn Russian: Прежде он работал в школе, теперь в банке. - He used to work at a school, now at a bank.

Both mean 'earlier' or 'in the past', and they are often interchangeable. However, прежде is slightly more formal than the very common раньше. It is often used specifically to set up a strong contrast between the past and the present.

Why do we use теперь for 'now' instead of the more common сейчас?

Сейчас usually refers to the exact present moment (right now). Теперь is used when comparing a new present situation to how things used to be in the past. Since this sentence contrasts his past job with his current one, теперь is the perfect choice.

Why is the verb missing in the second half of the sentence?

In Russian, it is very common to drop words in the second part of a sentence if they can be easily understood from the context. Instead of spelling out that he currently работает (works), the sentence simply says теперь в банке (now at a bank).

Why is the imperfective verb работал used here instead of a perfective form?

Working at a school was an ongoing state or routine over a period of time, not a single, one-time completed action with a specific result. To express the English idea of 'used to do something', you always use the imperfective aspect.