The other posts are correct, but I think there might be a bit of confusion, so I'll be very SPECIFIC.
If a parade or "fireworks show" is scheduled to start at PARK CLOSING TIME:
You will be stopped from ENTERING the queue at that exact time.
If you are already IN the queue, you will be allowed to wait your turn and ride that attraction. When the queue is finished (last person inline has ridden) the ride will be shut down to guests for the evening. (Even if the parade or fireworks are still going on).
If a parade or fireworks are scheduled at a time that is, say, 30 minutes or an hour (or more) BEFORE the park is scheduled to close, the ride will, of course, continue to operate normally during the fireworks show and/or parade.