Should a Parent or Guardian's Agreement to an Exculpatory Clause

Essay

Should a parent or guardian's agreement to an exculpatory clause on behalf of a minor be binding on the minor? Examples might be a parent signing such a clause on behalf of the minor for a school field trip (thus the parent is not present and the exculpatory agreement is signed prior to the undertaking of the activity)and when an entire family undertakes an activity together such as skiing,snowmobiling or white water rafting.What ethical issues are involved here?