Crossland High School is a high school in the town the series is set in. Greg's older brother, Rodrick, is a student there and in the online version, Rodrick's said to be a junior at the school.
It's apparently the only high school in the town that Greg lives in, because he's never referred to any other high school. In the original online version, the only other high school that's mentioned to be in Greg's town besides Crossland High School is Bishop Garrigan High School—for part of the online version, Greg's dad, Frank, considered enrolling Greg at Bishop Garrigan for high school, but ultimately decided against it after an incident with Bill Walter.
- Rodrick Heffley
- Heather Hills
- Lenwood Heath (Possibly)
- Ward (Online book)
- Andrew Hatley
- Bill Watson
- Unidentified Rodrick's Friend (i)
- Unidentified Rodrick's Friend (ii)
- Kathy Nguyen
- Leonard Harrington
Crossland High School doesn't appear physically in any of the books or the films, but it is mentioned several times in the books.
- In the original online version of the book, Greg expresses the desire to go to Crossland for high school instead of Bishop Garrigan, since Crossland's coed (meaning they have both male and female students) while Bishop Garrigan is an all-boys school.
- In the first book of the series, Greg and Rowley go to their annual haunted house with Greg's mom sometime near Halloween. However, Greg and Rowley discover that the house is much scarier than they imagined it to be, and while being chased by a guy in a hockey mask down a place called "Chainsaw Alley," Greg's mom stepped in and made the guy apologize and show them an exit.