@alonsov It depends on how students are marked in the SIS. For example: in Nebraska we have a specific state field we marked and then are able to search that field and pull the list of students. Do you have such a field?
@mimismith For Nebraska, S_NE_STU_X.Section_504
@alonsov Is there a reason you cannot search on that field to get your 504 students and then do a Quick Export/List of just them?
@mimismith The simplest way is to search on the field that "marks" the 504 students in PowerSchool. Many of the districts I work with use an alert and a checkbox, so one could search "alert_504#" to return all students that have the 504 Alert checkbox checked. In the case of Nebraska, as Heather mentions, they have a State field: S_NE_STU_X.Section_504, so you could search using that field.
Once you have your 504 students selected, you can do a List Students/Quick Export of any fields you'd like.
If you can do an advanced search on that field - you should be able to export to excel. In PA - the advanced search would look like this - AREA - Personal - Field Name - 504 Plan- Condition - = and Value - yes