A new law makes your involvement in your child's credit more important than ever. In recent years college students could get credit cards easily. Some 84% of under grads have at least one card., and many carry four or more. New legislation taking effect in February 2010 prohibits banks from issuing cards to those under 21 unless they have an adult co-signer or proof of means to cover payments. On the plus side, the restrictions will reduce the amount of card debt the average student racks up but cosigning could leave you with a big bill and a battered credit score if your teen flakes out.