This is the status level for what type of custody the inmate is classified most notably in the TDCJ system, but in other state systems as well. This designates where and what type of facility they will be housed. The line class levels from highest to lowest level are as follows: S1 - minimum custody, S2 - low custody, S3 - medium custody and S4 - maximum custody There are only a few of S1 facilities in the TDCJ. Most inmates are in S2 and it is as high as they will go. For some crimes (homicides in particular) S3 is as high as the prisoner can go. Generally, unit disciplinary cases are the cause of an inmate dropping in class. Inmates generally rise in class levels by serving their time incident-report free. How often and how many class levels a prisoners rises or falls is a decision made by unit authorities. Re-classifications occur every six months to a year.