My science-fantasy world has been devastated by monster attacks coming from various enormous pits in planet . The first lead to a total collapse of civilization and the next one, some 300 years later, lead to a more moderate collapse. Following these attacks, humanity has united in a global empire where service to the government and your community is a key value. Once people graduate high school, they are drafted into one of several programs. There's the military (which venture into these pits to decrease the number of monsters that could potentially erupt into the surface), national guard, police, and a public works department. The last one involves building/repairing infrastructure throughout the empire. People have a choice of which department they can join (unless there is a critical need for new members in one, necessitating a draft to that specific department), and most people choose the public works department because it has less inherent dangers (the police department from other people, and the national guard and military from monsters) and it has the potential to take you to different parts of the world. My question is: what kind of work could recent high school graduates do for the infrastructure of this empire when they have very little skills?
This fictional world is not Earth and is not connected in any way to Earth (it's not a future colony or anything of the sort) though the planet's size, geography and climate is Earth-like.
This world is futuristic, about 70 years ahead of our world in terms of technology.
Following the second collapse some 600 years ago there has not been another worldwide apocalypse, though there have been many attacks on individual cities/region within the empire by monsters (which is why the army and national guard are still so critically needed) which have at times completely destroyed cities or small regions. The reoccurring nature of these monster attacks is why the public works department exists.