Janet Yellen was a stellar student, named valedictorian and “class scholar" at her Brooklyn high school before studying under Nobel laureates for her economics doctorate.

Today, the Federal Reserve chair is facing her first daunting test on a world scale, as financial markets grow alarmed over slowing economic growth and an approaching shift in the Fed policy that she largely controls.

The Dow Jones Industrial Average shed nearly 1,000 points in less than three weeks while sustaining its worst three-day loss since the European debt crisis and U.S. debt-ceiling showdown of 2011. The Dow fell 5.5% from its Sept. 19 peak to 16,321 Monday, leaving it down for the year, before bouncing modestly on Tuesday.

While the market setback is hardly extreme after a five-year climb, the global nature of the current anxiety and its effect on everything from currencies to commodities to debt markets has raised the prospect that Yellen might soon face what has been called the “curse of the new Fed chief.”

The past three Federal Reserve chairmen all endured crises early in their tenures. A few months after Paul Volcker arrived on the job in 1979, the Iranian revolution prompted an oil-price spike, a nasty U.S. recession and a grueling inflation shock that required him to counter with punishingly high interest rates.

Alan Greenspan succeeded Volcker in August 1987, just in time for the October 1987 Wall Street crash, which cost the stock market 22% of its value in a day and threatened to snuff out the ‘80s economic boom.

Ben Bernanke ascended in the relative calm of early 2006 – right near the peak of the housing bubble. A few months later he presided over the last interest-rate increase the Fed has attempted, which was quickly followed by the unraveling of the subprime-mortgage market and ultimately the global financial crisis.

The recent market tumult hasn’t yet advanced to the level of drama and pain of those prior crises. Still, investors are registering deep concern over a broad set of related areas of vulnerability that reveal the fragility of the post-crisis economic recovery.

Nick Colas, market strategist at brokerage and research firm ConvergEx Group, says that for Yellen, “The test isn’t on her desk yet, but it is as if the teacher has just walked in” and is about to spring a pop quiz on the class.

As for what subjects will be on the quiz, markets are fixated on mounting risk of another recession in Europe, where German industrial output dropped sharply, hurt in part by sanctions on Russia over its Ukraine policies. European weakness is manifest in reawakened signs that deflation – or broad, growth-sapping price declines – is a nearby threat.

Meantime, Chinese economic performance has been spotty, world oil prices have been sinking fast and investors have flocked to the safety of U.S. government bonds, with the 10-year note yield falling to 2.22% from 2.62% on Sep. 18.

As the rest of the world has struggled, the value of the U.S. dollar has surged. This helps keep domestic inflation low, but causes pain in many developing economies that have dollar-based debt and depend on commodity exports to grow.

Coming after an unusually placid spring and summer, this wave of unease is washing over world markets just as the Fed prepares this month to end its two-year campaign of buying a total of $1.6 trillion in Treasury and mortgage bonds.

This is hardly a coincidence, as investors have grown at least psychologically dependent on the support of aggressive easy-money policies, which have lowered borrowing costs and encouraged risk-taking.

The monthly BofA Merrill Lynch Global Fund Manager Survey, released Tuesday, found: “Concerns over the imminent end of quantitative easing in the U.S. have left investors much less confident in the outlook for the global economy and corporate profitability.” These investors’ collective expectation that the economy will soon strengthen is at a two-year low.

The expiration of this so-called quantitative easing program has been well telegraphed by Yellen and her predecessor, Bernanke. Yellen’s message since taking office Feb. 3 has been firm and consistent. She has repeatedly cited a still-impaired labor market and has steadfastly said that, after QE ends, short-term rates will stay near zero for a “considerable period” - to be determined strictly by the strength of the economic data in coming months, not a preset timetable.

While her message has been clear, the ebb and flow of economic data and markets has whipped investor expectations around. As the unemployment rate declined beneath 6% in the spring, undercutting the Fed’s own forecasts for yearend, chatter got loud that Yellen would be forced to hike rates sooner.

With the recent market skittishness acompanied by tame inflation data, the conversation has flipped to whether Yellen might need to put off rate hikes indefinitely, and even to whether the Fed will neeed to alter its policy due to weakness overseas.

The Merrill Lynch survey found that investors’ view of central bank policy has not been this tilted toward a desire for further monetary stimulus since August 2012 – right before the Fed’s current QE program was launched.

The idea that Yellen might be moved to restart QE or even explicitly push out the likely date of a rate hike appears quite premature. The U.S. economy has continued to perform reasonably well, with growth running near 3% and job gains trending near a healthy 200,000 per month.

Yet there is little faith that Yellen’s counterpart at the European Central Bank, Mario Draghi, has the will or political support to follow the Bernanke-Yellen path toward aggressive easy-money efforts to stave off deflation and recharge growth on the Continent.

Ultimately, Draghi’s problem could become Yellen’s problem, should markets become more severely roiled and threaten the flow of credit and puncture business confidence in the U.S. This scenario would generate that tough test for Yellen – who is not central banker to the world, but who might be graded as if she were anyway.