This is a wonderful Valentine's lesson I found HERE on the Deep Space Sparkle website. It's great for teaching kids how to draw a heart as a form as opposed to a shape.
I gave kids a heart shape handout to practice on. They turned this into a 3D candy heart. They then traced this onto heavier paper. I gave them a choice of media to colour them: some used pencil crayons, watercolours, watercolour pencils or tempera paint. I demonstrated how to shade them using three different values: light, medium and dark.
Some Grade 4 - 6 results!