<?php
 
//метод в модели subjects
public function marks()
    {
        return $this->belongsToMany('App\Marks');
    }
 
//метод в модели students
    public function marks()
    {
        return $this->belongsToMany('App\Marks');
    }
 
//метод в контроллере SubjectsController
    public function show(Subjects $subject)
    {
        $students = Marks::where('subject_id', $subject->id)->get();
 
        dd($students);
    }

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