จัดกลุ่มนักเรียนด้วย LINQ

using System;
using System.Linq;
record Student(string Name, string Grade, int Score);
class Program
{
    static void Main()
    {
        var students = new[] { new Student("Ada", "A", 95), new Student("Lin", "B", 84), new Student("Grace", "A", 91) };
        foreach (var group in students.GroupBy(s => s.Grade).OrderBy(g => g.Key))
            Console.WriteLine($"{group.Key}: {group.Average(s => s.Score):F1}");
    }
}