To me, the message is that a centrally controlled society is, by its very nature, unjust and destructive of the human spirit. This is a very consistent theme in Lowry's works.
In this community, everything is run according to the "Way" and is administered by the Guardians. They essentially mandate the way people are to live. This leads to tremendous injustices such as the way people are killed for questioning or simply for deviating from the Way. This is why Kira's father has been driven away and has had to find the other village where he could live.
As in The Giver, Lowry is trying to show us that human beings must be free to pursue their own individual feelings, talents, and desires. Any society that tries to decide these things for them is unjust and destructive.
There are certainly plenty of messages or themes for you to identify in this great dystopian novel, but one of the more interesting ones is the presentatino of creativity and artistic talent. We are persented with a world where the grim struggle for survival has seemingly all but vanquished any latent spark of artistic expression in the humans that remain in this bleak post-apocalyptic world. However, the clear talent that Jo, Kira and Thomas have is presented in a supernatural way, as they are able to achieve great works of art through their talent seemingly taking control of them and directing their body. Note the way that Thomas's carving that he did when he was just a child and Kira's piece of cloth that she wove in a sense "made themselves."
The Council of Guardians recognises the potential power of creativity in the three children and are obviously attempting to use it for their own purposes, to fashion their own future. This, interestingly, creates a feeling of oppression in Thomas, Kira and Jo as they feel their talents being directed not along spontaneous and natural routes but towards a specific goal as they are wielded by the Council. Note Kira's frustration and her desire to weave her own patterns:
She wanted her hands to be free of the robe so that they could make patterns of their own again. Suddenly she wished that she could leave this place, despite its comforts, and return to the life she had known.
Artistic talent is thus presented as a true force to help change and develop the future, but at the same time it is a force that can be manipulated and used and not allowed to develop naturally.