How to get motivated to exercise/move around?

Im pretty fast in my class.But not the fastest.Yet i bearly excercise.I run alot at school and ran a 3km ace but bearly excercise...I think school was the only thing that excercised me now its summer break.I d swimming lesssons in the summer but thats not enough.Whats a fun way or a good ay to motivate me to excise? Im in elementary school and my parents have to work my 14 year old brother looks after us but all he does is play video games.I also mostly play video games.The only time i have fun running around/excising moving is when im with my friends :( But my parents have to work