If you are saving money for a child to go to college, make sure you know how it is invested.

This is no time to blindly count on the good graces of the stock market to help you pay for college tuition.

Instead, consider a rule of thumb in investing: Don't risk money in stocks or stock mutual funds if you will need to spend it within five years. That applies whether you have college savings in a 529 college savings plan, a Coverdell education account, or any other account set up for college.

The rationale comes from stock market history. The market goes into sharp losing periods, or bear markets, about every four to five years on average. And even the best and brightest pros on Wall Street have trouble predicting when those periods will occur, how long they will last, or how bad they will become.

Recently, the market fell 10 percent as analysts debated whether a strong global economy would be enough to prevent a U.S. recession and a further drop in the stock market. Stocks have rebounded some, but the market is up one day and down the next--a volatile period suggesting great uncertainty about the near future.

When serious downturns do occur, investors can lose a lot of money if they have to withdraw cash to pay a college bill.

Pulling money out of a vanishing stash eliminates some of the opportunity to gain it back when the stock market begins to heal. Stocks can fall sharply and remain down for a couple of years or even longer.

That's where the five-year rule of thumb comes from. Usually, stocks recover within five years, although there have been some instances when it has been even longer. So an investor who can wait for the rebound could be fine. But it can require patience, and you don't get patience when the college bursar's office wants a check. After hitting a record high before the 2000-02 bear market, it took the stocks of the Standard & Poor's 500 index seven years to get back to even.

To protect savings from being severely damaged by a bear market, financial planners have investors hold a mixture of stocks and bonds. With the combination, bonds provide insulation--taking the edge off the brutality of a falling stock market. Yet the stocks, which tend to grow a lot more than bonds over long periods of time, are there to perform that feat once the ugly period comes to an end.

If you have a 529 that automatically invests your money based on the age of your child, you probably have insulation from downturns built into your plan.

Typically, 529 plans have managers that invest all a family's college savings in stocks for babies, but as the child ages stock exposure is cut back and more bonds are added. By the time a student starts college, 529 plan managers often leave only 20 percent of the money invested in stocks.

If you have chosen to invest on your own in a 529 plan, or chosen what's called an "aggressive" investment option for your funds, you might have more exposure to stocks than is prudent.

You can easily remedy it by contacting the administrator of the 529 plan--often through the Internet, your state's education department, or the broker who might have sold you the plan. Under 529 rules, you can make a change in the investments once each year, said Joseph Hurley, publisher of SavingforCollege.com.

To figure out what mixture of stocks and bonds might be appropriate for your child, you can copy what 529 plans do with what are often called age-based investment options. You can find the plans offered by all states at www.savingforcollege.com.

Digging through Web sites can be difficult, so here's a model that might help you spot where your child might be.

Mutual fund company T. Rowe Price, which operates 529 plans in states such as Maryland and Alaska, invests 100 percent of a family's college savings in stocks for babies and toddlers. By age 7, stocks are cut back to 84 percent of the total college fund, and bonds make up 16 percent.

By age 13, the mixture is roughly half stocks and half bonds. You might think the family will be spending money for college in five years, and shouldn't have any stock investments. But remember, families typically don't spend all the college savings during the first year. At age 13, savings for college won't be spent entirely until nine years later. So some stocks remain necessary to help grow the pool of money.

By age 16, investing becomes quite cautious because a bear market could reduce savings at a time when the family cannot rebuild the stash adequately. Then, T. Rowe Price takes an extra step to protect the savings--14 percent is invested in a money market fund. Another 52 percent goes into bonds, which have the potential of growing more than a money market but can lose money occasionally. At this point, only 34 percent of the child's college money remains in stocks.

And two years later, as the child begins college, only 20 percent is in stocks and 34 percent is tucked safely into a money market fund. The remaining 46 percent is in bonds.

As you examine your college savings, consider making another contribution too. Several states will provide matching money each year you make a contribution. So depending on your income level, you might be able to obtain free money to help pay for your child's education. Some states give you a tax deduction for saving in their 529 plan, so the deduction--in effect--helps you save for college by cutting your taxes.

If you find out you haven't been receiving a tax deduction because you are saving money in a 529 plan offered by a state outside your own, you can remedy that. You can open a new 529 plan in your state and contribute to it and receive a deduction this year. You can continue to use that 529 and one in another state. If you want to move money from one state to another, Hurley said you are allowed to do that every 12 months.

Gail MarksJarvis is a Your Money columnist. Contact her at gmarksjarvis@tribune.com.