The boy doesn't have the endurance he needs to survive this.

Certainly he'll last an impressive amount of time for his age, but he won't make it out alive.

The Shredder suspects he has something else planned, considering that he is not fleeing and seems to be willing to experiment. He reacts to the charge by adopting a defensive stance, and when he reacts to the kick, it's by twisting his body to take the kick with his folded arms. He has to adjust his stance to account for the force. It's more like a cannonball shot to an armored tank. The force is strong but the hull is stronger.

And then, quickly, Shredder grabs for his ankle. If Jason doesn't move fast enough, he'll risk being swung aside like a ragdoll.