Final answer:
In a playful way, the children conspire against the governess by engaging in mischievous and secretive behaviors, such as stealing and acts of cunning.
Step-by-step explanation:
According to the governess, the children conspire against her in a playful manner by being mischievous and engaging in subtle yet clever acts of rebellion and deception. These acts are designed to be underhanded and secretive, like stealing books and records or engaging in acts of stealth and duplicity. The children's conspiring is not overtly harmful but rather displays a certain level of cunning, suggesting that their purpose might be more related to playful mischief rather than malicious intent.