string[] animals = {
    "alpacas", "capybaras", "chickens", "ducks", "emus", "geese",
    "goats", "iguanas", "kangaroos", "lemurs", "llamas", "macaws",
    "ostriches", "pigs", "ponies", "rabbits", "sheep", "tortoises",
};

plan_school_visit("School A");
plan_school_visit("School B", 3);
plan_school_visit("School C", 2);

void plan_school_visit(string school, int groups = 6) {
    randomize_animals();
    string[,] group = assign_group(groups);
    Console.WriteLine(school);
    print_group(group);
    Console.WriteLine();
}

void randomize_animals() {
    Random random = new Random();
    for (int i = 0; i < animals.Length; i++) {
        int r = random.Next(i, animals.Length);
        string temp = animals[r];
        animals[r] = animals[i];
        animals[i] = temp;
    }
}

string[,] assign_group(int group = 6) {
    string[,] result = new string[group, animals.Length / group];
    int start = 0;
    for (int i = 0; i < group; i++) {
        for (int j = 0; j < result.GetLength(1); j++) {
            result[i, j] = animals[start++];
        }
    }
    return result;
}

void print_group(string[,] group) {
    for (int i = 0; i < group.GetLength(0); i++) {
        Console.Write($"Group {i + 1}: ");
        for (int j = 0; j < group.GetLength(1); j++) {
            Console.Write($"{group[i,j]}  ");
        }
        Console.WriteLine();
    }
}