Your kitten will calm down maybe a small amount, but honestly that is debatable. Some cats become a little lazier and less hyper but most of them act like nothing has phased them. This does not mean that you shouldn’t bother to have them spayed or neutered! As a matter of fact, please have them fixed! You don’t want a male cat peeing on your stuff or a female screaming all the time when she’s in heat or pregnant. Like Bob Barker said, “spay and neuter your pets!”