Transpac/panam/aerogard (et al) has long been a foreign-pilot student-mill. Three students and one instructor in the airplane, just land to swap students. Instructors have record numbers of student-failures for practical tests; it's common for students to have multiple failures on each of their certificates or ratings. Deer Valley is the busiest general aviation field in the country. A lot of student operations out of there, very little intelligible English on the radio or the general area.
When a school only allows four of their aircraft to be used for solo flights, and most "solo" flights are done with the instructor on board ("supervised solo"), it doesn't speak particularly well to the confidence of the school.