overachiever


From The Collaborative International Dictionary of English v.0.48:

overachiever \overachiever\ n.
   1. A student who attains higher standards than expected based
      on the IQ score.
      [WordNet 1.5]

   2. A person whose achievements exceed what was expected based
      on his/her background, education, or mental ability.
      [PJC]
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