This would be a good question for a regional scientist. I'm modeling flows of students between school districts. A helpful reviewer pointed me to previous work that modeled such flows using spatial interaction models, otherwise known as gravity models.
I am a bit puzzled, because in Chun & Griffith (2019), in Chapter 7 on Spatial Interaction models, the toy data set includes flows of the number of workers among 6 counties in Texas. It also contains rows for the number of workers who worked in the same county with the origin id and the destination id the same county id for a total of 6 * 6 = 36 observations.
On the other hand, in Wolwer, Burgard & BreBlein (2018), the toy data set is one of trade volumes and it excludes the trade within countries.
It seems like since I am modeling students who stay or move, this is more analogous to workers, so I should include rows for students who stay.
I can't find explicitly direction in the literature as to the inclusion or exclusion of this.