On your Lessons page you will see that you have a Learning Rank, what does this mean?
Your Learning Rank is a score based on how many lessons you have done.
Each lesson is worth 1 point, and you will go up in rank every 10 points like so:
Pawn = 10
Knight = 20
Rook = 30
Queen = 40
King = 50
You can keep going up levels after King. Each additional 50 points gives you another King rank. For example, at 100 Lesson points you would reach King 2, and at 150 you would get King 3, and so on.
Keep doing lessons to get your King ranking!