Management.java

class Management {
  static listOfStudents = new ArrayList<Student>();
  public static void main(String[] args) {
    School wku = new School("Western Kentucky University");
    Student macha = new Student("macha", 10, 8, wku);
    Student mt = new Student("mt", 10, 8, wku);
    
    addStudent(macha);
    addStudent(mt);
    
    System.out.println("Total number of students: " + listOfStudents.size());
  }
  
  static void addStudent(Student student) {
    listOfStudents.add(student);
  }
}

School.java

class School {
  String name;
  
  public School(String name) {
    this.name = name;
  }
  
}

Student.java

class Student {
  String name;
  int rollNumber;
  int standard;
  School school;
  
  public Student(String name, int rollNumber, int standard, School school) {
    this.name = name;
    this.rollNumber = rollNumber;
    this.standard = standard;
    this.school = school;
  }
}