According to an expert in weightlifting, because teens are not yet fully grown, they should be careful to not put strain upon their skeletal structures which are yet developing. Older males, of course, have a fully developed skeletal structure and have a higher testerone level; therefore, they can lift more than their teen-age counterparts. So, teens, do need to be careful as mentioned above.
Likewise, for girls the same holds true regarding the developing skeletal structure. Of course, women do not in general have the strength of men, so caution is advised in their attempts. Working gradually and with trainers are the best method of weightlifting.