Knowledge of any foreign language is useful. especially knowledge of English. As This is well known fact that english is the means of communication between different people from different countries. This language unites us as humans. It gives us an opportunity to be closer to various people all over the warld. It gives us a chance to get new ways of global problem solving. Future of every ambitious person depends on it. So if you want your children to become succesful, they should learn english at early age. From one side children are easy-learning and accept language like a new game. From other one at early age children like sponge absorbs information automatically , effortless. So it would be logically to give them an opportunity to start learning English untill their brain is not restricted by well-known stereotypes that learning of any foreign language is hard work.