Instate of beating him, hug him!

 He just want your spacial attention. 7 year old is still very little. Give him one hour each day as a special time for him. List 100 good words about him with a big big hug.Be patient, and show your appreciation to him.  You will realize actually you have the best son in the world. Forget about piano or anything else. A happy child can do his best in every thing he like to do.

I have experience of a sad mother and a happy mother myself. If you like to discuss more, you are welcome to qqh me.