Nothing contained in this chapter shall be construed to conflict with the laws relating to child labor, nor to prohibit the establishment and maintenance of bona fide occupational qualifications, nor to prevent the termination or change of the employment of any person who is unable to perform his duties, nor to bar any organization operated for charitable or educational purposes, which is operated, supervised or controlled by, or in connection with, a religious organization, from giving preference to persons of the same religion or from making such selection as is calculated by such organization to promote the religious principles for which it is established or maintained.