Напечатать фамилии двоечников, посчитать процент успеваемости

struct School
    {
        public School(string surName, byte age, int schoolNumber, byte mathBall)
        {
            SurName = surName;
            Age = age;
            SchoolNumber = schoolNumber;
            MathBall = mathBall;
        }
        public string SurName { get; }
        public byte Age { get; }
        public int SchoolNumber { get; }
        public byte MathBall { get; }
        public override string ToString() => $"Фамилия - {SurName}, Возраст - {Age}, Номер школы - {SchoolNumber}, Оценка по математике - {MathBall}";
    }
    class Program
    {
        static void Main(string[] args)
        {
            School[] schools = new School[3];
            schools[0] = new School("Петросян", 14, 123, 5);
            schools[1] = new School("Мартиросян", 12, 123, 2);
            schools[2] = new School("Абрасян", 13, 89, 4);
            PoorStudent(schools);
            PercentageOfAcademicAchievement(schools);
            Console.ReadKey();
        }
        static void PoorStudent(School[] schools)
        {
            foreach (School student in schools.Where(e => e.MathBall <= 2))
            {
                Console.WriteLine(student);
            }
        }
        static void PercentageOfAcademicAchievement(School[] schools)
        {
            int five = schools.Count(e => e.MathBall == 5);
            int four = schools.Count(e => e.MathBall == 4);
            int three = schools.Count(e => e.MathBall == 3);
            Console.WriteLine($"Процент успеваемости: {((five + four + three) * 100) / schools.Length}%");
        }
    }