Depending on how long ago the whole school photograph was taken it could have been done in several ways. The Cirkut camera mentioned above and also the so called banquet formats could have been used. These banquet formats are still widely used by photographers today. These would have been the Folmer and Schwing, Korona, and even one of the Deardorff models. These would have been in the 7X17, 8X20, and the 12X20 formats.
It is my understanding that the Widelux is more current vintage.