How high does the championship levels go?

Hey we are in a guild challenge and there leader was level 21? I thought 20 was the highest how high does it go?
The championship level goes up by one every season. As there is no relegation the championship levels need to grow otherwise you'll end up with everybody on championship level 20. Top 9 players in the level 21 championship will get promoted to level 22 next season and so on and so on