In Gathering Blue by Lois Lowry, how is the value of human life addressed by the society in which Kira lives?

Perhaps the best insight into how Kira's community values human life is provided by Kira's trial. Vandara, Kira's accuser, brings a case against Kira that relies on the accepted standards of the community. 
"She was imperfect. And fatherless as well. She should not have been kept." The society believes that a child born with an imperfection, such as a disability, should be killed right after birth. They believe the spirit takes days to come into the child, and thus it is acceptable to kill a newborn infant. If a child cannot be provided for because it has no father, that child can be euthanized as well.
"She has not contributed." Humans are valued in Kira's society for contributing in material ways such as planting, weeding, or tending animals. A person who cannot perform a job that enhances physical existence may be killed.
"She can't marry. No one wants a cripple." Again, those who don't fit in or match the expectations of the society do not deserve to live.
"She causes problems with the discipline of the tykes, telling them stories, teaching them games so that they make noise and disrupt the work." The relational aspect of life, especially of the older people toward the children, is not valued in the society and is even considered a hindrance to the community. 
In Kira's defense, Jamison doesn't deny that Vandara accurately reflects the standards of the community. He says, "The accuser is correct that it is the way." The only defense he brings is that there may be exceptions. The Council of Guardians may violate the standards, but that does not nullify them. In their society, a person is valued for fitting in, for being able to perform jobs that sustain physical life, and for having normal looks and physical abilities. 
The society enforces its standards in the harshest way possible: by sending those who don't measure up to the Field of Leaving, where they will starve to death.