Complex sentence: After sending the image to the school's server, the laptop was programmed to erase the "sent" file created on the laptop, so that there would not be any trace by which students might realize that they were being watched and photographed.
Split into simpler sentences: After sending the image to the school's server, the laptop was programmed to erase the "sent" file created on the laptop. That way, there would not be any trace by which students might realize that they were being watched and photographed.