Cardio kickboxing classes don't provide self-defense skills but will improve your strength, endurance, and coordination.
However, kickboxing can be effective for self-defense if learned as a combat sport from a martial arts studio. The sport incorporates strikes like kicking and punching while also teaching you to defend against attacks. But unlike Jiu-Jitsu and similar martial arts, kickboxing doesn't incorporate grappling moves designed to help you escape an attacker who is holding you on the ground.