"Students' Performances" means the performances of several different students. "Student Performances" mean multiple performances done as student exercises. The second could mean multiple performances by a single student. It could also mean performances by people who are in the role of a student, but are not actually students, because here "student" is an adjective modifying "performances", while in the first form "students'" is a noun in the genitive case (often called a possessive) indicating an association betweeen the students and the performances.
Both are grammatical, and both correctly describe the content. Technically, the first form is more accurate because there are in fact multiple students performing, multiple performances, and the performers are all actual students. But these are all quite subtle points, and no viewer is in fact likely to be confused. Personally I would prefer "Student Performances" as much on the basis of sound as anything else.
If total accuracy is the goal, the title could have been "Performances by Students from Several Different Schools, 2019", or something else that spells things out more thoroughly.