The full GLSEN 2021 National School Climate Survey report includes information on LGBTQ middle and high school students' experiences, including: (1) Hearing biased language, from both students and educators; (2) Experiences of harassment and assault; (3) Anti-LGBTQ discrimination; (4) Effects of a hostile school climate on educational outcomes and psychological well-being; and (5) The availability and utility of supportive school resources. This report also examines demographic and school differences in students' experiences, and explores LGBTQ students' experiences with GSAs. In addition, this installment of GLSEN's National School Climate Survey also includes an exploration of how school climate has changed over time. Because this data is from the 2020-2021 academic year, when schools had to respond to the COVID pandemic, we also discuss key differences between the experiences of LGBTQ+ students in online only, in-person only, and hybrid learning environments. [For the executive summary, see ED625381. For "The 2019 National School Climate Survey: The Experiences of Lesbian, Gay, Bisexual, Transgender, and Queer Youth in Our Nation's Schools. A Report from GLSEN," see ED608534.]