BEIJING  Before the opening bell sounded on the New York Stock Exchange on a recent Tuesday, a group of fresh college graduates clocked in at a small trading firm on the outskirts of this capital city.

They were hired to engage in rapid-fire stock trading with some of the world’s most powerful investment houses in New York, London and Tokyo, and they were instructed to be alert.

“The market could be volatile today,” King Chan, the general manager at the firm, Lazer Trade, shouted to the group during a pep talk. “Be careful at the open. And don’t take dumb risks!”

Mr. Chan’s day trading shop is one of many that have sprung up in and around China’s major cities in recent years. Trading firms based in the United States and Canada are recruiting inexpensive workers in China and teaching them to engage in speculative trading  which means repeatedly buying and selling shares listed on the New York Stock Exchange and Nasdaq, hoping for quick profits.