If your kid is bored of doing home work or studying his text books, then the best way to renew his interest levels is by letting him play a game for an hour.
If the game is something that involves physical movement, it is better. A game like cricket or foot ball would do. When the physical body is worked out a bit, the brain becomes active too.
In fact, even a game like chess can refresh the bored mind of your kid. Play chess for a while with your kid and take him back to the study table to continue with the study.
In fact, choosing a physical activity would be a lot better as today's kids seldom get the chance to workout well. Physical activity helps in the growth and development of the kid.
It isn't advisable to force your kid to study when his mind isn't able focus at all. The best way to enhance your kid's productivity is by making him excited and refreshed.
But never choose activities like watching TV to refresh the mind of your kid as such activities do more harm than good. Only games that activate the body or the mind help your kid do well in academics.