This program is supposed to teach PE and also train children's brains in attention and focus. It has been recommended for Gifted kids with symptoms of ADHD.
This is not technically fully free. It's a "pay as much as you want" program that you can put in $0 for. You don't have access to the entire program for $0, but when you sign up it tells you what you have access to and what you have to pay for greater access (mostly of reports to help you assess your child's strengths and progress).