grant-student-product-access.php

// Where $email = your user's email address
// and $product_id = the ID number of the product you'd like to add them to

$zippy = Zippy::instance();
$user_id = email_exists($email);

if (!$user_id) {
    $student = $zippy->make('student');
    $student->username      = $$email;
    $student->email         = $email;
    $student->password      = wp_generate_password();
    $student->role          = 'subscriber';
    $student->register();
} else {
    $student = $zippy->make('student', array($user_id));
    $student->fetch();
}
// Claim the order on either the old or new student account
$zippy->access->claim($student->getId(), $product_id);