Disclaimer: The age ranges are not exact - we do not know the abilities of your actors!
This reflects our (imperfect) judgement of whether we think some groups of a particular age would be capable of performing the script and also that they would enjoy it!
This does not mean that we think all groups of the specified age would be capable of enjoying the script!
Sometimes, this depends on the purpose of the performance. For example, plays based on fairy stories do not necessarily appeal to teenagers, however performing the same show to a family audience may well appeal to those same teenagers!
Where we think that scripts are suitable for the under fives, it generally means that most of the lines will come from narrators, who will generally be older! (Whilst we know of a play narrated by a four-year-old, this would not be common practice!)
The "Mixed Adults and Kids" option checks to see if a piece was designed for a cast with a mixed age range.
The "Kids' show Performed by Adults" category exists for those few shows designed to be performed to an audience of children, generally with adult performers.
(This is a different category from a "family show" in that it is unlikely that the adults in the audience would get much out of the show!)
In summary, these categories exist to help you narrow down your search; they do not guarantee that a script is suitable for your group!