Querying information from multiple tables based on the user currently logged in

I am using Laravel 5.6 and trying to query information from the grading_info table but I also want to return the students name and other info from the student_info table. I only want to return records in the grading_info table that are related to the currently logged in teacher. Currently its returning information for all teachers. I know I can add a where clause but I am trying to learn eloquent and was wondering if there was any way to accomplish this?

Teachers and students can have many enteries in the grading_info table and any teacher can grade any student.

I would like to return something like this

    {
        gradeID,
        gradeDate,
        gradeInfo
        .....
        student: {
            studentName,
            studentPhoneNumber,
            studentEmail
            ......
        }
    }

users table (only stores teachers, not student)

• id

teacher_info

• teacherID (linked to id from users table)

student_info

• id (auto increment. not relation to the users table)

grading_info

• studentID (linked to id from student_info)
• teacherID (linked to id from users)

User model

public function grades(){
    return $this->hasMany(GradingInfo::class, 'studentID');
}

GradingInfo model

public function teacher(){
   return $this->belongsTo(User::class, 'id', 'teacherID');
}

public function student() {
    return $this->belongsTo(StudentInfo::class, 'studentID', 'id');
}

StudentInfo model

public function grades() {
    return $this->hasMany(SessionInfo::class, 'studentID', 'id');
}

TeacherInfo model

   // Nothing in here. 

TeacherController

public function getGrades(Request $request)
{
    $user       = Auth::user(); // This is the teacher
    $grades  = $user->with('sessions.student')->orderBy('created_at', 'DESC')->get();
   return response()->json(['sessions' => $sessions], 200);
    }