On library day, I would go straight to the mystery drawer of the card catalog. I remember a series about a group of kids who had a clubhouse in an old bus buried under piles of junk in one of their families’ junk yard. They got in and out through a tunnel they had dug. They had a trap door in the floor of the bus. They would have adventures and solve mysteries. I don’t remember the name of the series. This would have been 1981 or 1982. Also, the Hardy Boys and Nancy Drew.