(CNN) -- GLAAD has released the ninth edition of its annual Network Responsibility Index, and for the first time, a major TV network has received a grade of "excellent."

Fox got that rating for its LGBT-inclusive content, which the responsibility index maps. Examining programming that aired between June 2014 and May 2015, the study gave Fox and ABC Family its highest ranking.

The achievement is all the more golden for Fox given that in 2006, the network received a failing grade in the inaugural report.

GLAAD Chief Executive Officer Sarah Kate Ellis announced that this would be the final National Responsibility Index as her organization seeks to focus on increasing diversity among the LGBT images found in television.

"GLAAD's Network Responsibility Index has helped reshape the television landscape, inspiring LGBT characters and storylines that move acceptance forward," Ellis said in a statement. "As representations of LGBT people in the media continue to rise in number, pushing television networks to make those representations more diverse is more crucial than ever. This requires a different set of tools than the NRI provides, and as such GLAAD will shift focus to its annual TV diversity and transgender reports."

Fox had the highest percentage of LGBT-inclusive original programming hours, with 45.4%, which also was the highest percentage GLAAD has tracked on a broadcast network since it began compiling the index. The network also had the most racially diverse representations on broadcast TV, with 36% of its LGBT impressions made by people of color. That number is notably helped by its hit show "Empire," which features a prominent black gay character.

ABC Family posted the highest percentage of LGBT-inclusive programming for any network tracked by the index previously. Of its original programming, 74% included LGBT characters, with 79% of those lesbian characters and 49% people of color. The network also featured a transgender character played by a transgender actor.

In terms of racial diversity among LGBT characters, The CW led, with 38% of impressions being made by people of color. It also had the second-highest percentage of inclusive programming hours, with 44.8% of its original programming hours including LGBT people. And although The CW also had the highest percentage of LGBT impressions, GLAAD deemed many of the impressions to be "minor" rather than "major."

The CW received a grade of "good," as did ABC, FX, HBO, MTV and Showtime. CBS, NBC, TLC, TNT and USA were ranked "adequate," while the A&E and History networks both received a "failing" grade.

GLAAD plans to continue to release its Where We Are on TV, Studio Responsibility Index and Transgender Images on TV reports. The Where We Are on TV report analyzes the diversity of prime-time scripted series regulars on broadcast networks, while the Studio Responsibility Index maps the quantity, quality and diversity of LGBT people in films released by seven major studios. The Transgender Images on TV report, which will be released in November, catalogs and assesses the quantity and quality of transgender images on television.

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