Green’s Dictionary of Slang

(US campus) a student with a negative or objectionable attitude; also attrib.

1965		J. Hersey Too Far to Walk 37: Breed with his total nego outlook [HDAS].
1979		G. Wolff Duke of Deception (1990) 185: The rest of us – ‘negos,’ carpers, corner-cutters, and wise-apples – bucked the system and had some fun.