My son started with Kurt at the end of Y8 with one trial. He's been good at Maths since he was little. Before going to Kurt, he did entrance test at end of Y7 for Y9 class with almost full mark but quit from Du after two trial lessons as he didn't like the content.
With Kurt, the questions are more challenging and he finds interesting and is actually learning something new.
My suggestion: if you are mid level or not very keen on Maths, don't go to Kurt. The fast paced & level could make you more frustrated.
If you fail the class test than you need to have a detention before class to repeat until you pass. It's good to help you grow but bad if you're mentally fraigile.