The study examined the effect of parental involvement on students' mathematics achievement. The investigator selected four Algebra I classes taught by one teacher and randomly placed two classes in the control group and two classes in the experimental group. The parents of the students in the treatment group received monitoring sheets twice a week, that contained students' scores on daily homework and test grades, but the parents in the control group did not receive monitoring sheet. Students in the experimental group outperformed the students in the control group. With respect to gender, the results showed that parental involvement did not affect student achievement differently. Lower achieving students, in the experimental group significantly outperformed such students in the control group.