The law does say they will take the Oath to get the Certificate (but it may be waived for the very young or incompetent). It is an opportunity for good public relations and good press to do a kind of a ceremony for a bunch of kids.....
INA 341 CERTIFICATES OF CITIZENSHIP OR U.S. NON-CITIZEN NATIONAL STATUS; PROCEDURE
(a) A person who claims to have derived United States citizenship through the naturalization of a parent or through the naturalization or citizenship of a husband, or who is a citizen of the United States by virtue of the provisions of section 1993 of the United States Revised Statutes, or of section 1993 of the United States Revised Statutes, as amended by section 1 of the Act of May 24, 1934 (48 Stat. 797), or who is a citizen of the United States by virtue of the provisions of subsection (c), (d), (e), (g), or (i) of section 201 of the Nationality Act of 1940, as amended (54 Stat. 1138; 8 U.S.C. 601), or of the Act of May 7, 1934 (48 Stat. 667), or of paragraph (c), (d), (e), or (g) of section 301 of this title, or under the provisions of the Act of August 4, 1937 (50 Stat. 558), or under the provisions of section 203 or 205 of the Nationality Act of 1940 (54 Stat. 1139; 8 U.S.C. 603, 605), or under the provisions of section 303 of this title, may apply to the Attorney General for a certificate of citize nship. Upon proof to the satisfaction of the Attorney General that the applicant is a citizen, and that the applicant's alleged citizenship was derived as claimed, or acquired, as the case may be, and upon taking and subscribing before a member of the Service within the United States to the oath of allegiance required by this Act of an applicant for naturalization, such individual shall be furnished by the Attorney General with a certificate of citizenship, but only if such individual is at the time within the United States.