Dear Christine, I agree with John R, at common law (and under some state laws) a contract made by a minor is voidable, except in a few situations as described by John above.
Contracts not in these categories are voidable at law - in that the contract will and may continue in force until or unless avoided by the minor, however the minor remains bound by any obligations arising under the contract up until that point.
Minors can however ratify a contract once they turn 18.