In thinking about this topic your license for doing a show is much like renting a car from Avis.    Let's say you rent a Toyota Corolla.   Your rental agreement gives you the right to drive the car and you agree to reasonably take care of it while it's in your possession.   It doesn't allow you to paint a racing stripe down the middle or to remove the Toyota logo from the hood.   It's still a looks and runs like Toyota Corolla so why should Avis be upset?   I think the answer is painfully obvious. 

Originally posted by sconjott Some lines, lyrics, even small words seem inconsequential but you try telling that to the person who may have thought about using the word "the" in a particular seen for 2 weeks that it didn't matter and doesn't change the show in the slightest.

Although you cannot change anything without permission, with a lot of publishers, doing a play in the school setting comes with understanding.  I have never directed a kids play exactly exactly as it was written, and I've always been able to get permission.  Most of the time, my changes have been adding characters (very minor parts) or adding a made up song to a non-musical.  Call and talk to the customer service people when you order scripts.  Community groups that I've worked with have had more difficulty than I have in the school setting with this.  Its so hard to find the perfect play for an always changing number of kids that asking is really the only way to get a script perfect for that group.  Good luck!

So, when an actor - on-stage during a performance - forgets a line and another actor steps in to help get everyone back on track, does that constitute changing the show?

This is interesting. I just got my copy of Every Christmas Story Ever Told (And Then Some!) from Playscripts, Inc. and it contains the following production notes:

"The script is peppered throughout with topical references and a few local/theatre specific references, which by the time your production roles around might be as topical as the Chia Pet, so feel free to update them (for the love of God please update them). Likewise, think of the script as an all-cotton sweatshirt: stretch it to fit the particular quirks and talents of your cast, crew and audience."

However, I'm somewhat curious about whether or not the playwrights have legal permission for all the riffs on Christmas television specials including snatches of songs. Are you allowed certain latitude with parody in this case?