JFLEG
JHU FLuency-Extended GUG corpus
TextsCC BY-NC-SA 4.0
JFLEG is for developing and evaluating grammatical error correction (GEC). Unlike other corpora, it represents a broad range of language proficiency levels and uses holistic fluency edits to not only correct grammatical errors but also make the original text more native sounding.
Source: JFLEG: A Fluency Corpus and Benchmark for Grammatical Error Correction