I think you have the key order incorrect in the Student model. You need to pass the foreign key first.
public function belongsToMany($related, $table = null, $foreignKey = null, $otherKey = null, $relation = null){}
//Student model
public function coffers(){
return $this->belongsToMany('App\Models\Coffer', 'coffer_student', 'student', 'coffer_id')->withPivot('status');
}
On a side note, you don't need to list the table or key if they follow the convention that the table is derived from the alphabetical order of the related model names (coffer_student), and should have, in this case, the student_id and coffer_id columns.
//Student model
return $this->belongsToMany('App\Models\Coffer')
->withPivot('status');