This is a really interesting question. To be honest, I hadn't associated this excellent dystopian novel with the category of bildungsroman, which can be referred to as a novel of education or development. Bildungsroman novels typically present us with a young, childhood narrator who is naive and has experienced some form of great hardship. However, through the course of the novel, and the trials and tribulations that the main protagonist endures, they find their place in the world and become a meaningful member of society.
what is interesting about this novel is that I feel that David lacks something of the independence and headstrong nature that is characteristic of protagonists in bildungsroman novels. He is presented as a character that is led by others rather than leads. You might want to consider the impact of other characters such as Michael, Uncle Axel and Rosalind on him and how he seems quite happy to go along with what others tell him to do. However, having said this, the novel makes it clear that he develops from quite a naive young boy to becoming, necessarily, a young man who is aware of the very dangerous position he is in and how one wrong move could be his last. He likewise through his trials finds his place in the world - even if it involves leaving Waknuk and flying to Sealand.
So, all in all, I think it is very helpful to view this novel as a kind of bildungsroman, though it is necessary to be aware of the drawbacks of such an approach as I have identified above. David as a character lacks the vibrancy and strength of other protagonists in bildungsroman novels such as Jane Eyre or Pip.