You can easily study at home. A 'child' in this context is usually does not have a choice in the matter, where as when one becomes an 'adult', you have the choice of going or not. For college classes, it really depends on the class and the professor. Some teach straight from the book, with nothing extra added to the cirrculum. In this case, it depends on if you prefer to hear the professor speak or read on your own time. If the professor includes participation and/or custom lecture notes only available if you come to class, then it is probably in your best interest to go, assuming there is nothing more important that needs to be done. Even if you do not go to the latter class, it does not necessarily mean you are 'childish'. You can copy the notes from someone else and/or you can study on your own and try your best. It is more about responsibility than 'doing' or 'not doing'.
