Harsh Realities: The Experiences of Transgender Youth in Our Nation’s Schools

This report from GLSEN (Gay, Lesbian, and Straight Education Network) takes a close look at the problems faced by transgender students, who have some of the most horrifying crimes committed against them. This article was also made with the help of several transgender persons, so the language is more politically correct than some other resources. This is a great source for transgender-related statistics.
Length: Medium (under 100 pages).
(direct link)
(diigo link) 

Students' and Teachers' Perspectives on School Climate

This link from GLSEN (Gay, Lesbian, and Straight Education Network) is presented on the host site, instead of linking directly to the report. On the blue sidebar on the site, there are links to not only the full report, but also the executive summary, and individual reports from ten different states. This is a very useful, well-organized source, especially for statistics. I would recommend using this as a main source for LGBTQ+ statistics in education. It also includes statistics about underlying problems: why students are harassed, why so much bullying is not reported, ect.

Length: Long (over 100 pages).
(direct link)
(diigo link)

Playgrounds and Predjudice: Elementary School Climate in the United States

Another excellent source from GLSEN (Gay, Lesbian, and Straight Education Network), this report details the problems facing LGBTQ+ students, and students with LGBTQ+ family and presentation in American elementary schools. This also has a wealth of information on teacher responses to LGBTQ+ related bullying.

Length: Long (over 100 pages).

(direct link)

(diigo link)

THE EXPERIENCES OF LESBIAN, GAY, BISEXUAL AND TRANSGENDER MIDDLE SCHOOL STUDENTS

This "research brief" from GLSEN (Gay, Lesbian, and Straight Education Network) is an excellent resource for statistics about bullying and other difficulties in American middle schools (junior high). Some of the report focuses on the availability of in-school LGBTQ+ resources, and works to compare some situations to the statistics from high schools on the same issues. 

Length: Short (under 25 pages).
(direct link)
(diigo link) 

The Principle's Perspective 

This report from GLSEN (Gay, Lesbian, and Straight Education Network) shows excellent statistics on how principles of elementary, middle, and high schools see the treatment of LGBTQ+ students. This article clearly shows disparities between the perspectives of LGBTQ+ youth and the figures of authority above them, and thus should be used as a supplemental source.

Length: Long (over 100 pages).
(direct link)
(diigo link)