In the mornings Joseph teaches the children of Little Lamplight who voluntarily want to learn. He usually teaches them the history of Little Lamplight as well as subjects such as basic Math and English. He also occasionally teaches the children survival skills. If the player talks to Joseph, he tells them that he obtained his teaching materials from Holodisks that were taken from the classroom inside of Vault 87. Since all access to the Vault has been cut off, the children have been learning the same things for generations.
The player is capable of receiving a haircut from Joseph.
If the player rescues Joseph's sister Penny from Paradise Falls as part of the Rescue from Paradise quest line, you can ask Joseph to bring you to a locked door that when opened leads you directly into Vault 87. To open the door you need Joseph to turn on a terminal which you can then hack. This effectively saves you from having to venture through Murder Pass, an areas swarming with Super Mutants.
Another way to get Joseph to turn on the terminal is to ask Mayor MacCready if there is an alternate route into Vault 87. He will then tell the player to talk to Joseph to gain access to the computer.