Индекс за пределами диапазона

private void FillExampleData(DataContext context)
          {
            Educator [] educators = new Educator [] {
                new Educator() { Id = 1, FirstName = "Иванов", Name = "Иван", LastName = "Иванович", Email = "edu01@localhost", Password="pass01", Position = "Воспитатель", Qualification = "4 уровень", Phone = 422115, Experience = 5},
                new Educator() { Id = 2, FirstName = "Петров", Name = "Пётр", LastName = "Петрович", Email = "edu02@localhost", Password="pass02", Position = "Директор", Qualification = "5 уровень", Phone = 425652, Experience = 6 },
                new Educator() { Id = 3, FirstName = "Наумова", Name = "Анна", Email = "edu03@localhost", Password="pass03", Position = "Повар", Qualification = "3 уровень", Phone = 444555, Experience = 9 },
                new Educator() { Id = 4, FirstName = "Васильева", Name = "Мария", LastName = "Семеновна", Email = "edu04@localhost", Password="pass04", Position = "Воспитатель", Qualification = "4 уровень", Phone = 456544, Experience = 4 },
                new Educator() { Id = 5, FirstName = "Мелкова", Name = "Светлана", LastName = "Игнатовна", Email = "edu05@localhost", Password="pass05", Position = "Воспитатель", Qualification = "4 уровень", Phone = 444555, Experience = 8 },
                new Educator() { Id = 6, FirstName = "Сернова", Name = "Алёна", LastName = "Валерьевна", Email = "edu06@localhost", Password="pass06", Position = "Няня", Qualification = "4 уровень", Phone = 444555, Experience = 9 },
                new Educator() { Id = 7, FirstName = "Антонов", Name = "Аркадий", Email = "edu07@localhost", Password="pass07", Position = "Воспитатель", Qualification = "4 уровень", Phone = 444555, Experience = 2 },
                new Educator() { Id = 8, FirstName = "Миронова", Name = "Тамара", LastName = "Александровна", Email = "edu08@localhost", Password="pass08", Position = "Зам.директора", Qualification = "5 уровень", Phone = 556302, Experience = 7 }
         };
            
            context.SaveChanges();
 
            Administrator ad = new Administrator() { Email = "admin001", Password = "admin001" };
            context.Users.Add(ad);
 
            context.SaveChanges();
 
            Parent [] parents = new Parent [] { 
                new Parent() { Id = 1, NameMom = "Мамаева Алена Дмитриевна", JobMom = "Школа искусств, учитель рисования", PhoneMom = 226484, NameFather = "Мамаев Иван Петрович", JobFather = "Станция ТО, директор", PhoneFather = 548911 },
                new Parent() { Id = 2, NameMom = "Усова Мария Сергеевна", JobMom = "Школа №2, учитель", PhoneMom = 844463, NameFather = "Усов Александр Матвеевич", JobFather = "Школа №2, учитель", PhoneFather = 487944 },
            };
            
            context.SaveChanges();
 
            Group [] groups = new Group [] {
                new Group() { Id = 1, Name = "A-04-05" },
                new Group() { Id = 2, Name = "B-07-08" }
               };
            
            context.SaveChanges();
 
            Children [] childrens = new Children [] {
                new Children() { Id = 1, FirstName = "Мамаев", Name = "Игорь", LastName = "Иванович", Date_Birth = Convert.ToDateTime("15.05.2005"),  Groups = groups.ElementAt(1), Parents = parents.ElementAt(1), Date_In = Convert.ToDateTime("01.09.2006"), Date_Out = Convert.ToDateTime("30.05.2011") },
                new Children() { Id = 2, FirstName = "Усова", Name = "Анастасия", LastName = "Александровна", Date_Birth = Convert.ToDateTime("17.11.2005"),  Groups = groups.ElementAt(1), Parents = parents.ElementAt(2), Date_In = Convert.ToDateTime("01.09.2006"), Date_Out = Convert.ToDateTime("30.05.2011") },
                new Children() { Id = 3, FirstName = "Мамаева", Name = "Александра", LastName = "Ивановна", Date_Birth = Convert.ToDateTime("24.09.2007"),  Groups = groups.ElementAt(2), Parents = parents.ElementAt(1), Date_In = Convert.ToDateTime("01.09.2008"), Date_Out = Convert.ToDateTime("30.05.2014") },
                new Children() { Id = 4, FirstName = "Усов", Name = "Петр", LastName = "Александрович", Date_Birth = Convert.ToDateTime("14.01.2008"),  Groups = groups.ElementAt(2), Parents = parents.ElementAt(2), Date_In = Convert.ToDateTime("01.09.2008"), Date_Out = Convert.ToDateTime("30.05.2014") }
            };
            
            context.SaveChanges();
 
            ClassJob [] classjobs = new ClassJob [] {
                new ClassJob() { Id = 1, Name = "Рисование", Educators = educators.ElementAt(1), Time = 35 },
                new ClassJob() { Id = 2, Name = "Развитие речи", Educators = educators.ElementAt(5), Time = 40 },
                new ClassJob() { Id = 3, Name = "Прогулка на улицу", Educators = educators.ElementAt(7), Time = 30 }, 
                new ClassJob() { Id = 4, Name = "Логические игры", Educators = educators.ElementAt(5), Time = 40 },
 
            };
            context.SaveChanges();
            context.Educators.AddRange(educators);
            context.Childrens.AddRange(childrens);
            context.ClassJobs.AddRange(classjobs);
            context.Groups.AddRange(groups);
            context.Parents.AddRange(parents);
                     
            context.SaveChanges();
        }