I was wondering if there are equivalent instructions for drawing a face side-on (something that kids are bound to ask about eventually!) so I had a quick google, compiled some of the guides I found, looked at a few faces, and came up with the following.
Draw a circle and halve it. The halving line can stick out slightly past the bottom of the circle.
Depending on which way the person you're drawing is facing, draw two lines on one side of the face to represent the chin. The chin should extend below the circle.
Taking into account the entire height of the total face (not just the circle), halve it.
Then quarter it.
Then divide the bottom quarter into eighths.
Add the outline of the nose and forehead. The forehead should end at the top quarter (this is where the hair will begin). The nose will go from the bottom to the top of the third quarter. The exact shape of the nose/forehead will depend on the person you are drawing.
Draw a rectangle from the bottom eighth to the half-way line, so that it includes the nose.
Draw a vertical line to halve this new rectangle, then draw the diagonal. These green lines will show you where to draw the eye, nostril and mouth.
Add the eye so it touches the line-half way up the face and starts at the vertical green line, as shown. The exact positioning of the facial features will depend on the person you are drawing.
Draw the nostril so it lines up with the diagonal green line.
Draw the outline of the mouth and chin. The chin should be in the bottom eighth of the face, the mouth should be in the second-to-bottom eighth of the face. Look at the person you are drawing for the exact shape of the mouth and chin (generally the nose will stick out over the lips, which will stick out over the chin).
Extend the mouth inwards until it hits the diagonal green line.
Draw another box in the second-to bottom quarter as shown, and halve it.
The ear will sit so it is touching the pink halving line, as shown. The ear should be around the same hight as the nose, but this will depend on the person you are drawing.
Drawing the inside of the ear could be very confusing for primary school children. I used this as a guide.
Children may prefer not to draw all the detail of the ear, to make things simpler.
Add the hair so that it starts at the line marking the top quarter. The exact shape of the hair will depend on the person being drawn.
Add the neck.
Remove guiding lines and ta-dah, done!