Prep School is an unmarked quest in Fallout 4.
Bunker Hill is a wealthy trader hub that relies on paying raiders off to get by and survive. Mayor Kessler isn't proud of the arrangement, but it's the best they can do, especially with Judge Zeller and his "Army" skulking around. However, if a freelancer comes by who proves they aren't just slinging drugs or robbing people, she might just use them as a deniable asset if they prove themselves, wiping out Zeller without tying the attack to Bunker Hill.
- After completing Traffic Jam, Deb will refer the player to Kessler for more work. The mayor will explain that she needs a problem solver who doesn't do them by way of drugs or indiscriminate violence. She needs a deniable asset who can direct violence in the direction of Zeller at the East Boston Preparatory School. There's no opportunity to haggle for a higher payment.
- Head to the School. The objectives are to kill Zeller and rescue any captive traders or caravan hands found there. The School is a fairly confusing maze of corridors, but both Zeller and the three caravan captives are located on the top floor, on opposite ends. Lockpick the doors to the captives' cells and talk to them to release them from captivity, then kill Zeller.
- Return to Kessler