Teachers take educating people as their personal duty.
Tips
grammar
Almost always seen in the literary frame 以…为己任 ('to take X as one's own duty'). Plug a verb phrase into the slot: 以天下为己任 (take the world as one's duty), 以救国为己任, 以教书育人为己任.
history
The frame echoes 《论语·泰伯》: 士不可以不弘毅，任重而道远。仁以为己任，不亦重乎? ('A scholar must be broad-minded and resolute, for his burden is heavy and his road is long. He takes humanity as his duty - is that not weighty?'). The Confucian root explains the phrase's serious moral tone.
