HSM2: School's Out makes two show stops. During the show stop, the cast performs for approx. 18 minutes.
The first show stop is at Sunshine Plaza, not too far from the entry turnstiles. This is the more popular (i.e. crowded) of the two show stops and people generally start sitting on the ground around 30 minutes before the show time.
When the first show stop is finished, the traveling float then goes into "parade mode" as it makes its way up the performance corridor to the second show stop. During this time, the cast continues to sing "What Time Is It" in an endless loop.
The second show stop is by the Golden Dreams Theater. You can generally find a "front row" seat about 15 minutes before the show time. If no one is sitting down yet, find a CM and ask them which "line" in the pavement is the front of the seating area. This show stop eventually gets as crowded as the first stop, just not as early.
BlueBayou made a really good note above. The last show time of the day, the sun can get in your eyes if you're facing towards Condor Flats (1st show stop) or the Golden Zephyr (2nd show stop).
caldad, I hope you and your family enjoy the show!!!
Adding: the Orlando Sentinel reported that the Florida version of HSM2: School's Out will go dark in mid-September as they refresh the show for HSM3: Senior Year--which opens on Oct. 24. If this is true, I would guess that the DCA version would do the same.