The plot of A Kestrel for a Knave covers a day in the life of the main character Billy. A kestrel is a species of small falcon birds in the genus Falco. A plot is specifically the way events relate to each other; conflict is essential to the relationships that comprise plot. With this groundwork lain, we know that the main plot points will correspond to the major conflict points.
The first major conflict is Billy's unpleasant relationship with his heartless and cruel older brother Jud, who punches Billy first thing in the morning and continues throughout the story to be profoundly cruel to him. Jud is also related to the second major plot point that Jud has sold his bicycle and therefore has to struggle on his paper route, which is symbolic of trying to struggle against the odds to get ahead in life.
The third major plot point, which, you recall, encompasses conflict, is Billy's difficulties with his mother who was unfaithful to her husband, the brothers' father, causing him to leave. Central to the story is the kestrel about which we learn in a flashback. The farmer on whose land Billy finds the kestrel takes an interest in Billy's hunt for the kestrel and allows him to trespass while even helping him look. The kestrel figures strongly in the meaning of the book since it is in the title.
The next main plot point is that Billy has an awful lot of trouble of all sorts at school. This conflict culminates at his Youth Employment Meeting where Billy declares he has no hobbies that the Youth Employment Officer can help him turn into a job. Of course, his care and taming of the kestrel could have opened a few doors for Billy.
Finally, the conflict with his brother Jud comes to a head and precipitates the most dramatic plot point, that being the murder by Jud of the kestrel. The story is very bleak. It seems the high note is that the father punched the man with whom his wife was betraying him and walked out. Billy has little ahead of him except escape from the family his father left him with. Maybe he can find his father and then the two honorable men of the family can share their lives together.
[eNotes doesn't yet have Study Guides for A Kestrel for a Knave by Barry Hines but below are two reliable links, one to a GCSE English Literature study guide and one to a BBC interview with Barry Hines.]