Can you please give us a little more information so we can best answer your question? Was this a statement on the report card or said during a teacher/parent conference? What grade level or subject area was this stated?
If I had to guess, it could mean that the student wasn't participating as much as the teacher would like. For example, if the student is sitting a conversational French class where participation is necessary.
So if you can give us the context in which this term was used, we can probably give you a better response.
"Partial participation (Baumgart, et al., 1982) is another strategy for adjusting curriculum to facilitate the educational inclusion of students with severe disabilities . Partial participation, also known as multi-level instruction (Falvey, Givner, & Kimm, 1996), consists of allowing a student with a disability to participate in the same projects and instructional activities as the rest of their class, with specific modifications to the activity so that it suits a student's specific abilities and needs (Baumgart, et al., 1982; Falvey, et al., 1996)." (http://aim.cast.org/learn/historyarchive/backgroundpapers/promise_of_udl/what_curricula).
In essence, the partial participation strategy is based upon the notion that all students can learn. As such, all students should be included all activities irrespective of the fact that they may not be able to do it independently. Baumgart, D. & Brown, L., et al. (1982) The Journal of the Association for Persons with Severe Handicaps, 7, 17-27.