There are a few similarities. Both Billy and Beka have problems in their schools. Beka questions some of the Catholic beliefs and the Sisters of Charity threaten to expel her. Billy has lots of problems at school, is often sent to the principal's office, and is even caned.
In both novels, the stories are told using flashbacks. Beka's story begins where it ends, but in between, are multiple flashbacks that unfold her story and what happens to her and her friend Toycie. Billy's story is also told with many flashbacks to events that have happened to him in the past.
Both Billy and Beka are troubled young people that face many issues at home and at school and both characters do a lot of growing up in the novels.