Call to a member function associate() on null

    public function englishExams(): BelongsToMany
    {
        return $this->belongsToMany(EnglishExam::class, 'english_exam_student');
    }

    public function students(): BelongsToMany
    {
        return $this->belongsToMany(Student::class, 'english_exam_student');
    }

  Repeater::make('englishExams')
                            ->relationship()
                            ->schema([
                                Select::make('english_exam_id')
                                    ->label('English Exam')
                                    ->options(EnglishExam::all()->pluck('title', 'id'))
                                    ->required(),
                                TextInput::make('speaking_score')
                                    ->label('Speaking Score')
                                    ->numeric()
                                    ->required(),
                                TextInput::make('reading_score')
                                    ->label('Reading Score')
                                    ->numeric()
                                    ->required(),
                                TextInput::make('writing_score')
                                    ->label('Writing Score')
                                    ->numeric()
                                    ->required(),
                            ])
                            ->columns(4)
                            ->label('English Exams'),