Public schools are about 52 percent white, 16 percent black, and 24 percent Hispanic. (Hispanic students get counted as Hispanic no matter what their race.) If students were assigned to school completely evenly, all white students would be in schools that were (barely) majority white. Students of other groups would be in the minority. Of course, American schools are much more segregated than that. I’ve made a chart using data from the Digest of Education Statistics.
While most white students are in majority white schools, the fraction who are not is gradually growing. Some part of this is due to the increasing number of Hispanic students in the U.S. Some part is probably due to real decreases in de facto segregation.
On the other hand, the majority of Hispanic students and nearly half of black students are in schools where they make up the majority.
We can ask a somewhat different question: What fraction of students in a group receive substantial exposure to students from the other groups. The government reports the fraction of each group in schools where that group makes up more than 90 percent of the student body. Students in this situation may not get a whole lot of cross-group exposure. For blacks and Hispanics the fraction in this “mostly segregated” class is between 15 and 20 percent. The fraction hasn’t changed much in 20 years, having dropped a little for black students and risen a little for Hispanic students.
Unsurprisingly, white students are much more likely to go to school in this “mostly segregated” situation. The good news is that the fraction of mostly segregated white students has dropped substantially.