If you are playing in a jazz band next year and you have no knowledge of chords and scales I would highly recommend getting a private teacher.
To play jazz well you have to have a good knowledge of these things:

The major scale
the modes of the major scale
the melodic minor scale
7th chords
extensions of 7th chords (9ths, 13ths etc)

It would be pretty hard to explain them all on the forums so yeah, find a teacher or at least someone who knows about these things and learn them!