I work as a classroom assistant at a primary school in Salford and prison is a recurring subject. I'm not saying that all schools are the same, but this particular one I work at, prison is often spoke about because quite a high number of children either have a parent in prison or they have previously had a parent in prison.
Certain children can be bullied because of it especially if the crime has been reported in the local newspaper.
Society has changed and prison is becoming more of a talked about subject in schools. Years ago, schools used to have a local policeman come in to them and talk to the children about the consequences of committing crime. Sadly, this seems to be a thing of the past. High schools now see PCSO'S patrolling dining area's to deter crime. Many high schools now have Police presence. Personally prison is not an uncommon thing these days.