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.