I don't know what the demographics of your area are, but where I am parents are more than willing to pay for good after school activities. You aren't like an adult gym which just provides the facilities, you are providing a service, and (presumably) a safe and structured environment for kids. Any gym which provides training services charges a lot for this, whether it is an MMA gym or a personal training environment.
I understand the concept of a business plan that projects a loss for a while until getting established, but your model seems to be putting you in the hole from the start. What you are proposing should cost more than $50/month.