You got me curious so I did some Googling over my morning coffee. I found this article from the Library archive about black schools in Springfield. The Lincoln school operated in Springfield until 1955 when the schools became integrated.

Here's a little portion about the Lincoln school and I think that's who these marchers represent. "Springfield's most well-known Black school is the second Lincoln School at the southwest corner of Sherman Avenue and Central Street. Funded in part by an $8,000 grant from the Julius Rosenwald Foundation, it opened in 1931 with 15 rooms, including a library and a gymnasium. When the Douglas School, another Black school built in 1892 at the west side of South Market Avenue south of Lombard Street, closed in 1932, its students were transferred to Lincoln. The second Lincoln School remained in operation into 1955. After the landmark Supreme Court decision Brown vs. the Board of Education ruled that the segregation of schools was unconstitutional, Black students entering the 1954-1955 school year were given their choice to attend either a formerly white school in their neighborhood or continue to attend Lincoln School. Lincoln High School's 1955 senior class was the school's final group of graduates.

When Springfield integrated all of its schools during the 1955-1956 school year, the Lincoln School's name was changed to Eastwood Junior High School. In the fall of 1962 the building became the Vocational Technical School. In 1991, the building became part of Ozarks Technical Community College. OTC renamed the building Lincoln Hall in 1998 to honor its early history. Lincoln Hall has remained in continuous use for college courses."

So interesting!