This depends on the course you want to take.
To take the 102 you must have attended the 101 but do not have to have completed the jumps. (Therefore, bad weather on a 101 will not prevent you from taking the 102.)
To take the 103, you only need to have your B license. You do not need to have attended any prior Flight-1 course.
To take the 200 or 300 level courses, you must meet the minimum required jumps for each course outlined here. We do highly recommend that you have attended and completed the prior courses, but are not required to.
However, to take the 201A, you MUST have attended AND completed the 101 AND 102. To take the 202A, you must have attended and completed the 201A (and therefore the 101 and 102).