Working on JSON objects in jQuery and MVC

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using JsonMVC.Models;
using JsonMVC.Repositories;

namespace JsonMVC.Controllers
{
    public class JsonOperationsController : Controller
    {
        // Utility function to add a exam to each class for a list of students
        private void AddAnExamToStudents(IList<Student> students, string updateSource)
        {
            Random rd = new Random();
            foreach (Student aStudent in students)
            {
                foreach (Class aClass in aStudent.ClassesTaken)
                {
                    IList<Exam> exames = aClass.ExamesTaken;
                    Exam aExam = new Exam();
                    aExam.ExamTime = System.DateTime.Now;
                    aExam.Description = "Exam No. " +
                        exames.Count.ToString()
                        + " by " + updateSource;
                    aExam.Score
                        = Convert.ToInt16(60 + rd.NextDouble() * 40);

                    exames.Add(aExam);
                }
            }
        }

        [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult GetStudents(int NoOfStudents,
            int NoOfClasses, int NoOfExams)
        {
            StudentsRepository repository = new StudentsRepository();
            repository.Initialize(NoOfStudents, NoOfClasses, NoOfExams);

            return Json(repository.GetStudents());
        }

        [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult AddAnExamByJson(IList<Student> students)
        {
            StudentsRepository repository = new StudentsRepository();
            repository.SetStudents(students);

            AddAnExamToStudents(students, "json");
            return Json(students);
        }

        [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult AddAnExamBySession()
        {
            StudentsRepository repository = new StudentsRepository();
            IList<Student> students = repository.GetStudents();

            AddAnExamToStudents(students, "session");
            return Json(students);
        }
    }
}