According to history…this has happened many times. The most prominent example is that of the Greek Spartans (ca. 600-300 B.C.). The government would take away boys at age seven and put them through rigorous military training (hmm…very reminiscent of Ender’s Game). They did so in order to sustain the order of their society (i.e. their exploitation of the Messenian helots, who oftentimes liked to revolt). As a result, Sparta produced the greatest fighting force known to Greek history.
Did these young Spartans lose their childhood? I think not. The procedure ascribed to a normal childhood in their society was to be taken away and become soldiers. This was widely accepted. Mothers proudly gave up their children in order to promote the greater good. I think the same analysis can work with Ender’s Game. Was their culture wrong in establishing this system? That’s debatable. However, they did what they thought best to sustain themselves and provide a future for their children – even if this meant creatively using their children (what we might call exploitation of children). Overall, I think the “right to a childhood,” whatever that may be, is designated by the specific needs of a society and cannot be compared with how we might view a normal childhood today. However, I personally believe in the Golden Rule: do unto others as you would have them do unto you. Thus, I think the best society is one which incorporates this rule, especially in the raising of their children.