In addition to payback by the other party as mentioned by @nxtblg , one might also consider the ability of the one attempting to create the dilemma to enforce it.

In the above given example, if one child knows the following, they might well decide to remain silent even if they know the other will surely try to oust them:

• They have a right to attend school
• The other child cannot prove that they did anything

In real life having enough knowledge (and gumption) can make staying silent the best choice in many cases by creating a scenario where the perceived cost/pain of enforcement is too high for the ones presenting the dilemma.