Latino history is overwhelmingly left out of United States history textbooks, according to a new report.

The study from the Johns Hopkins Institute for Education Policy and UnidosUS, a Latino advocacy and research organization, identified key topics in Latino history to identify in teaching materials. Of the 222, only 28 were covered -- leaving 87 percent of Latino topics out of US high school history textbooks.

These topics include "many aspects of the Mexican-American War, the Spanish-American War, the U.S. acquisition of Puerto Rico, the Panama Canal, the modern civil rights movement, Cold War politics, and legal developments shaping the Latino experience, such as the Voting Rights Act, the Civil Rights Act, and racial segregation."

In K-12 schools across the nation, over a quarter of students are Latino.

Topics that received the most coverage included land purchases from Mexico, as well as Latin American foreign policy. Coverage was the "thinnest" from 1821 to the present, with the only event from the last 200 years that received coverage being Justice Sonia Sotomayor's appointment to the Supreme Court as the first Latina justice.

The report also noted that when topics were included, the coverage was "intellectually flat," omitting the impact of polices and events on communities in the past and into today.

Researchers called for publishers to develop textbooks "that fully expose students to the experiences of Latinos, incorporating rigorous content including both primary and secondary sources. At a minimum, publishers should commission independent reviews of their texts, measured against the seminal content."

Viviana López Green, senior director of the racial equity initiative at UnidosUS, said in a statement that "as the country grows more diverse, it’s essential for our future workers, businesspeople, community leaders, and public officials to learn about the contributions and experiences of all Americans, including Latinos, the country’s largest racial/ethnic minority.”