A substantial portion of the money going into tax-sheltered accounts, he argues, would have been saved anyway.

The investments grow in a tax-sheltered account and withdrawals are not subject to federal taxes as long as the money goes for education.

Zero-coupon bonds and funds invested in them are generally best for tax-sheltered accounts.

Any of these plans is a good deal compared with investing outside a tax-sheltered account.

A spokesman for T. Rowe Price said the information could confuse investors with tax-sheltered accounts.

"Each person has an incentive to shop around and save because you can keep what is left at the end of the year in a tax-sheltered account."

Munis are useful for people who can hold the bonds outside of tax-sheltered accounts.

New tax-free savings accounts - The few people who could afford it would be able to put upward of $60,000 a year into tax-sheltered accounts.

"If you take a big loss in a tax-sheltered account, you can't write it off," he said.

Or, you put into a tax-sheltered account more than you can legally.