Main.c#

public class Student
{
    private string name;
    private int age;

    public Student(string n, int a)
    {
        name = n;
        age = a;
    }

    public void ValidAge()
    {
        if (age >= 11 && age <= 16)
        {
            Console.WriteLine("Age Valid");
        }
        else
        {
            Console.WriteLine("Age Invalid");
        }
    }

    public string GetName()
    {
        return name;
    }

    public void SetName(string n)
    {
        name = n;
    }

    public int GetAge()
    {
        return age;
    }

    public void SetAge(int a)
    {
        age = a;
    }
}

public class P16_Student : Student
{
    private bool ucas;

    public P16_Student(string n, int a, bool u) : base(n, a)
    {
        ucas = u;
    }

    public override void ValidAge()
    {
        if (base.GetAge() >= 16 && base.GetAge() <= 19)
        {
            Console.WriteLine("Age Valid");
        }
        else
        {
            Console.WriteLine("Age Invalid");
        }
    }

    public bool GetUCAS()
    {
        return ucas;
    }

    public void SetUCAS(bool u)
    {
        ucas = u;
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        P16_Student stu24 = new P16_Student("Fei", 17, false);
        Console.Write(stu24.GetName());
        Console.Write(" is ");
        Console.WriteLine(stu24.GetAge());
        Console.WriteLine("UCAS complete: " + stu24.GetUCAS());
        stu24.ValidAge();

        P16_Student stu25 = new P16_Student("Bram", 12, false);
        stu25.ValidAge();

        Student stu1 = new Student("Bram", 12);
        stu1.ValidAge();
    }
}