Consumers Union has just trained its heavy guns on companies selling life insurance to college students. In CU's opinion, insurance for most students is an unnecessary expenditure, and those few who need it would do better with a regular policy rather than one designed for collegians. Needless to say, the companies in the business think this a cheap shot.

The fundamental question is whether students should be insured at all. In general, the companies argue that insurance, like spinach, is good for nearly everyone; Consumers Union thinks it should be bought principally by those with specific financial obligations to dependents, which lets most students out. Here is the substance of the debate.

Parents have a big financial investment in their children. It makes sense for the child to carry insurance naming the parent as beneficiary, so that if he dies the parent will be reimbursed.

If you think life insurance as a lottery, this is as good a reason as any for buying a policy. God forbid that your child should die, but is he does, you might as Well have an insurance payoff as not. The price of $10,000 in campus term coverage ranges from $20 to $40 a year.

But do you really feel that your child owes you the cost of his education (not to mention his room and board for 20 years)? If so, why not carry a policy on his life when he's 30 and 40, as well as when he's 20? The fact that parents don't insure older offspring indicates that most of them don't really expect to get their investment out in dollars and cents. But they are vulnerable to that sales pitch during the years they're actually scrimping to pay tuition.

If a student buys a term policy that is convertible into straight-life, and if he gets a rider that entitles him to buy more insurance in the future at standard rates, and if he becomes uninsurable by contracting a dread disease, or enters a risky occupation like stunt piloting that would make it hard for him to get insurance, then the policy he was prescient enough to buy in college may be the only coverage he can get.

Insurance agents argue that if you buy a straight-life policy now, you'll save money, because the premium is lower when you're younger. However, since you pay the premiums longer, and in the meantime lose the earning power of that money, the true cost of coverage is about the same no matter when you buy. The cost of straight-life is much higher than term, running from $150 to $300 for a person in his early twenties, depending on the company and the option chosen.

It is an article of faith with insurers that a straight-life policy is the cornerstone of family security and should be bought as soon as possible, perhaps even before you have any dependents to protect. Its purpose is to help you save money. (But there are other forced-savings vehicles available; also, people in all but the highest tax brackets will get a higher after-tax return on savings left in a credit union or bank term account.)