The usual word for disobedient but generally harmless behavior is mischief. Note that this is a collective noun: Tom Sawyer commits mischief, commits five mischievous acts, or is known for his mischievousness, but he does not commit five mischiefs.

Children known for their mischief may alternatively be known for their high jinks, monkeyshines, or naughtiness, or they may be guilty of shenanigans or tomfoolery.

The usual word for disobedient but generally harmless behavior among children is mischief:

1. bad behaviour (especially of children) that is annoying but does not cause any serious damage or harm
   2. the wish or tendency to behave or play in a way that causes trouble

Note that this is a collective noun: Tom Sawyer commits mischief, commits five mischievous acts, or is known for his mischievousness, but he does not commit five mischiefs.

Children known for their mischief may alternatively be known for their high jinks (energetic behavior), monkeyshines (playful tricks), or naughtiness (disobedience), or like adults they may be guilty of shenanigans (mildly bad or dishonest behavior) or tomfoolery (foolish or silly behavior).