CourseWork/app/Models/Grade.php

<?php

namespace App\Models;

use Illuminate\Contracts\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsToMany;

class Grade extends Model
{
    use HasFactory;

    protected $fillable = [
        'name',
    ];

    public function subjects(): BelongsToMany
    {
        return $this->belongsToMany(Subject::class);
    }

    public function scopeFilter(Builder $query): void
    {
        $name = request('name');

        $query->when($name, function (Builder $query, $name) {
            $query->whereRaw('name ilike ?', ["$name%"]);
        });
    }
}