Children Throwing Tantrums

my 5 year old has been having his fits since he started kindergarten...crying and whinning when he doesnt get his own way...i turn the tv off and make him sit on the sofa for 15 minutes...its not working yet but i do it every time..hopeing he will get it..its very annoying. he gets happy good boy notes from school but now acts out at home.....i cant send him to his room either too many toys and stuff in there .