This is the 7285th most frequent German word.
gefängnissen
"Gefängnissen" is the dative plural form of "Gefängnis," meaning "prisons."
In this sentence, 'Gefängnissen' is used in its plural dative form to indicate the locations where educational programs are available.
In vielen Gefängnissen gibt es Bildungsprogramme.
In many prisons, there are educational programs.
Here, 'Gefängnissen' is in the plural dative case to show the places associated with the inmates.
Die Insassen in den Gefängnissen erhalten Unterstützung.
The inmates in the prisons receive support.
In this usage, 'Gefängnissen' is implied in contrast as a variation of its nominative form, emphasizing the various types of prisons by this discussion.