Your son’s PR Card application will show up in the system once it is assigned to an officer and he or she is working on it. Until then, it won’t appear. The likelihood is that it just wasn’t assigned yet when you called.
To get urgent processing, you usually need to provide a purchased ticket. But it is possible that in this special situation, with an itinerary and a letter from the school, they may process it urgently. (This is at the discretion of the officer.)
You should wait until 190 days have elapsed and, if the card is still in processing, then consider submitting proof of urgency.