On May 7 2009 at the Coors Field in Denver, Colorado, the world's largest physics lesson was conducted.
The largest physics lesson involved 5,401 participants who were taught by Steve Spangler Science (USA) during a presentation at Coors Field in Denver, Colorado, USA, on 7 May 2009. The event was part of the 9News Weather & Science Day hosted by Steve Spangler and Kathy Sabine. Guinness World Records™ Adjudicator, Danny Girton, was present at the event to award the new record.
You can also read more about it here.
The question is, how effective was it rather than simply being a gimmick to get into the World Record book?