Children are property of their parents or the state until they
  are 18 years of age in many jurisdictions.

  They are the responsibility of their owners until such time that
  they are deemed fit for society. They cannot sign papers. They
  are not responsible for their actions. They are legally,
  infants. Infante.

  There are exceptions for certain things; infants are considered
  responsible for certain crimes. Also, some of the protections
  they have as infants they no longer have as older infants. But
  they're still legally infants.