Does a board have to have a meeting to schedule a special meeting or cancel a meeting?

No; the board does not have to meet to schedule another meeting. ORS 332.045 states that meetings can be called in the following ways (for K-12 districts): by the board chair, upon request of three board members, or by common consent of board members.

There is no requirement in public meetings law to notify the public if a meeting is canceled, but it is certainly recommended when it is known. Sometimes, however, it isn’t known in advance that a meeting will be canceled.  For instance, a meeting is scheduled, but a quorum of the board is not present at the meeting.  This meeting is effectively canceled.  When the board knows in advance that a meeting must be canceled, OSBA recommends posting the cancelation in the same places that meeting notices are posted.