Классы — Петр Могилов

<?php
class Student {
    public $fio;
    public $subjects;
    public $gender;
    public $group;

public function __construct($fio, $subjects, $gender, $group) {
        $this->fio = $fio;
        $this->subjects = $subjects;
        $this->gender = $gender;
        $this->group = $group;
    }

public function avg() {
        $total = 0;
        foreach ($this->subjects as $subject => $grade) {
            $total += $grade;
        }
        return $total / count($this->subjects);
    }
}

$students = [
    new Student("Прокопьев Александр Викторович", ["математика" => 33, "русский язык" => 93, "химия" => 72], "М", "МБ-103"),
    new Student("Рубцов Данил Петрович", ["математика" => 73, "русский язык" => 83, "химия" => 93], "М", "МБ-102"),
    new Student("Раева Ангелина Альбертовна", ["математика" => 96, "русский язык" => 96, "химия" => 96], "Ж", "МБ-112"),

];

usort($students, function($a, $b) {
    if ($a->avg() < $b->avg()) {
        return 1;
    } elseif ($a->avg() > $b->avg()) {
        return -1;
    } else {
        return 0;
    }
});
foreach ($students as $student) {
    echo $student->fio . ": " . $student->avg() . " балла<br>";
}
?>

Results:

Раева Ангелина Альбертовна: 96 балла
Рубцов Данил Петрович: 83 балла
Прокопьев Александр Викторович: 66 балла