  We describe a study of period changes in 59 RR Lyrae stars, using times of
maximum brightness from the GEOS database. The work was carried out by
outstanding senior high school students in the University of Toronto Mentorship
Program. This paper is written in such a way that high school or undergraduate
physics and astronomy students could use it as a guide and template for
carrying out original research, by studying period changes in these and other
types of variable stars.
