Have you considered how you are going to go sailing after taking classes? Doesn't sound like your parents sail or own a boat, or you'd probably have experience sailing with them. Look for a club or organization that has boats you can sail. They'll almost certainly offer lessons as well. If you were on the other side of the country, an organization like this one
would be a great choice.
At your age you'd be better off looking for dinghy or small boat classes rather then keel boat certification. If for no other reason that you aren't going to find a place that will let a 13 year old take out keel boats. You'll probably enjoy dinghy sailing more too.