I think that there are some elements that need to be addressed in this particular question.  Erikson would suggest that there has to be greater explanation as to the conditions and circumstances in which an adolescent has to work.  For Erikson, one of the primary developmental elements that must take place during the adolescent time period is to search for an identity of self.  The question of what constitutes one's identity is seen in light of external conditions such as peer recognition and understanding of oneself in the light of both social and personal notions of the good.  Working for 20 hours a week can be seen as a part of this process.  Yet, I think that some questions must arise.  If the adolescent is working as a primary wage earner or is working in a condition in which their own self- reflection is precluded because of earning wealth, he might voice some objection to such a condition.  At the same time, Erikson believed that the crisis of self- identity during adolescence is a fluid one.  Adolescents "sample" different notions of self and identity until something that can be appropriated is found.  This is a form of a "psychosocial moratorium," in which individuals are able to discern their own sense of self without great punishment or challenge. If this is precluded because of the element of work, Erikson might voice challenge or objection.  For Erikson, nothing should preclude the adolescent search for self, as this is the time period in which such questions have to be addressed and resolved in order to address the next crisis of emotional intimacy in love that awaits after adolescence.  If working so many hours in a week precludes addressing the issue of identity, Erikson would not be in strong advocacy of it.