Portrait Drawing Course week 1

Today I began a portrait drawing course at the SCCC under Pina Bartolo's tutelage. I've recently begun some portraits but struggled to get a likeness and thought that it would be great to get some direction/ ideas from a professional.

There are 16 persons in the class which made it very crowded. It probably is not possible to do painting given the space constraints. It would be nice if we could, though. There are easels everywhere and Pina could hardly move around the room.
Our model is Olivia who is of possibly hispanic background. Olivia is beautiful but in a sulky way. Her expression at rest is one who is comtemplating some minor grievance... although I am sure she is a nice a person, really.
Today's lesson is to get the structure right. Because we focus so much on features in other people, it is a bit of a struggle to draw them because we immediately dive into drawing the features. In reality features take only a small percentage of the head. To make it look realistic, we have to draw the shapes of the head, neck and shoulders convincingly or else it does not look plausible. This is a similar lesson to that in life drawing - geometry first to 'set the scene'.