You might hear: "You can not make me," or the quieter version, simply not moving. Defiance at this age usually reflects a Choice, Connection, or Competence gap. Something in their experience of the situation does not feel fair, does not feel connected to anything meaningful, or feels beyond what they can do. Understanding which one is happening points toward the response.
I hear you do not want to. I am curious about why. Can you tell me what is going on?