By the time your children toss their high school graduation caps into the air, they'll probably have chosen a college and mapped out their freshman courses. But is their health insurance securely in place?

Often, the medical plan a parent has through work will cover children up until they're between 20 and 24 years old, whether they live at home or away at school. However, because college health plans at some schools are subsidized by tuition (though not necessarily subsidized for the student's spouse or dependents), college plans might save parents money. If you don't have any health insurance for the student, college health plans could be a good solution.

College plans are not free, and the benefits vary from college to college. Committees from each college meet with insurance companies and design plans specific to their schools.

College plans sometimes limit preventive care, but students often can go to the college health center for free services. Many times there's no charge for office visits to the health center, although students may be charged for lab work, physical therapy, X-rays, prescriptions, and procedures such as treatment for a wound. Other covered services may include mental health, well-child care, newborn and infant care, routine pap and pelvic exams, cholesterol screening, and routine STD/AIDS testing. Mammograms are usually covered when prescribed by a doctor.

Typically, the school insurance provider may pay 100 percent of the cost for health center services, but for coverage outside of the health center, including out-of-state providers, a student's coverage may drop to 70 percent and impose a deductible. However, this may not be the case with every school. But according to Elaine Whetzel, administrator of the Student Health Center at Georgetown University in Washington, D.C., there are exceptions.

"If a student needs radiology services across the street, then they might have to pay a copayment," she says. "Most campus health centers are not equipped with lab facilities, so often those tests have to be sent out."

Dorothea Lyores, a spokesperson for Quincy, Mass.-based University Health Plans Inc., a nationwide student insurance provider, says that the degree of coverage varies from school to school.

Pre-existing conditions can create problems

Under some state laws, college health plans can refuse to provide benefits for the treatment of medical conditions that existed before the coverage took effect. So before you sign up for a college health plan, make sure you know how pre-existing conditions are defined.

According to Stephen Beckley, a principal at Hodgkins Beckley Consulting, LLC, an education health care management and benefits consulting firm concerned with higher education in Fort Collins, Colo., "The states are a checkerboard when it comes to pre-existing conditions," he says. "College plans are regulated under the same basis as an employee health insurance plan. Some states waive pre-existing conditions after six months of enrollment and some do not. It is important to read the fine print and understand how preexisting conditions apply to your insurance plan."

Beckley adds that because most colleges are funded by the federal government, medical underwriting is not allowed under federal law, so college health plans can't be priced according to a student's health.

People sometimes buy a college's health insurance even when the student is covered under a parent's plan if the parent policy requires doctor referrals for care. Obtaining referrals across states can be problematic. (Many HMOs require referrals for visits to out-of-network providers.) Parents who want their out-of-state college children to get prompt care without calling home for a physician's referral might want to consider college health plans.

Cost and the problem of referrals shouldn't prevent the student from having health insurance, whether it's through a parent's plan or the school's plan. A serious illness or injury could have long-lasting negative financial consequences for the student, the parent or both.