In the novel Never Let Me Go, do the guardians feel any sympathy for the children? How is lying to someone protecting them?
For one, consider that the faculty and staff at Hailsham are asking the same question you are: What should the children know? What's ethical for them to know? What's right? You might look specifically at how Miss Lucy and Miss Emily's approaches differ and how they speak with the children and reveal (or don't reveal) the truth.
A central theme to Never Let Me Go is identity -- what makes a human being a person, an individual? What is a soul and what nourishes a soul? And what happens in a world where the society has literally created people who aren't recognized as individuals with autonomy and agency? Kathy, Tommy, and the others are nurtured as children for a very specific purpose; they are valued because their bodies ensure prolonging the lives of their copies. How is this social structure ethical? How is it moral? Remember, though, that ethics and morality are subjective, so such conversations are always complex. You mention the lies and deceit, and you're right: there's a lot of it in this novel. However, is it better that the children know or not know what waits for them from the beginning? Lying is, in one way, a kindness, giving them hope for the future and the same sense of self any other child might have. If they were told the truth from day one, could children cope with the knowledge that they're simply "spare parts"? How would that impact their development? Is it better or worse that they know personhood before becoming part of the system? Is it better to rebel against the system or to accept fate?
Ishiguro uses his narrative to provoke such questions from his readers. So, you're on the right track here. To go even deeper, you might ask what similarities you see between Kathy's world and ours and what that suggests about what Ishiguro wants readers to take away from the story.