The Catholic conference warned that such sex education can have an effect on the school's general atmosphere.
"Parents can opt their children out of classroom instruction, but they cannot opt them out of schoolyard discussions and the culture change that may take place at school as the result of (comprehensive sexual health education)," warned the flier.
The flier cited the Second Vatican Council document Gaudium et Spes, which stressed the need to safeguard the right of parents to "educate their children in the bosom of the family."
In Nevada, voters can decide whether to change the state constitution's definition of marriage.
In 2002, over 67% of Nevada voters voted in favor of a marriage amendment defining marriage as a union of one man and one woman in the state constitution.
On this year's state ballot is Question 2, titled "Marriage Regardless of Gender," which would repeal the 2002 measure. It would require the State of Nevada and its political subdivisions to recognize marriages and issue licenses to "couples, regardless of gender."
Regardless of the state constitution, the state now follows the definition of marriage mandated by the 2015 U.S. Supreme Court decision Obergefell v. Hodges. By a 5-4 vote, the Supreme Court required that all states allow same-sex unions legally recognized as marriages.
Backers of Question 2 have said there have still been legal challenges against legally recognized same-sex marriage based on state constitutional definitions, such as an effort earlier this year in Tennessee which argued county clerks were wrong to distribute licenses to same-sex couples.
While Nevada's 2020 ballot measure recognizes the rights of clergy and religious organizations to refuse to perform a marriage, this is an area rarely contested in the courts. Rather, the legal redefinition of marriage has posed significant religious freedom problems for religious organizations, schools, social services, adoption agencies, businesses and individuals that do not recognize same-sex unions as marriages.
Question 2 was placed on the 2020 Nevada ballot after two consecutive sessions of the state legislature voted to place it there.
The Nevada Catholic Conference was not available for comment. The Diocese of Carson City did not respond to CNA's request for comment. The Diocese of Las Vegas did not have comment on Question 2 specifically, but a spokesperson noted that Bishop George Leo Thomas of Las Vegas recently said Pope Francis has been consistent in his belief that "marriage is a union between a man and a woman... It's the nature of things."
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Thomas' remarks came in the context of clarification after confusion regarding a video including footage of the pope's remarks on civil unions for same-sex couples.