Code first mapping issue while using Table per Hierarchy (TPH) - entity-framework

Question

For past few days we started to work on code first, as a part of that i faced one issue while doing mapping which i summarized here with different example. It would be more helpful if i got any solution
for that.
Below are the three entities
Course -> Entity holds information about course like fee, description etc and each course will
belong to some category or Type(i.e.. student, employee etc), It will refer to the person for whom registration is made with the help of ParentId and Type column
Example : To get the coursejoined by the student with ID 10, the sql query would be
"select * from course where type=1 and parentid=10"
Student : CourseJoined entity here should fetch only related record of type student (ie..1) same apply for Employee too
So first how to achieve that first?
I have tried to implement TPH logic here as below but i am getting exception
public enum CourseType
{
Student = 1,
Employee = 2
}
public class Course
{
public int ID { get; set; }
public int ParentID { get; set; }
public decimal Amount { get; set; }
public CourseType Type { get; set; }
public string Description { get; set; }
}
public class StudentCourse : Course
{
}
public class EmployeeCourse : Course
{
}
public class Student
{
public int ID { get; set; }
public string Name { get; set; }
public virtual ICollection<StudentCourse> CourseJoined { get; set; }
}
public class Employee
{
public int ID { get; set; }
public string Name { get; set; }
public string WorkingAs { get; set; }
public string Experiance { get; set; }
public virtual ICollection<EmployeeCourse> CourseJoined { get; set; }
}
Exception:
The foreign key component 'ParentID' is not a declared property on
type 'EmployeeCourse'. Verify that it has not been explicitly
excluded from the model and that it is a valid primitive property.
2) To avoid that error i removed the ParentID from Course table and
placed them in StudentCourse and EmployeeCourse after that i found below migration script
CreateTable(
"dbo.Course",
c => new
{
ID = c.Int(nullable: false, identity: true),
Amount = c.Decimal(nullable: false, precision: 18, scale: 2),
Type = c.Int(),
Description = c.String(),
ParentID = c.Int(),
ParentID1 = c.Int(),
})
.PrimaryKey(t => t.ID)
.ForeignKey("dbo.Employee", t => t.ParentID, cascadeDelete: true)
.ForeignKey("dbo.Student", t => t.ParentID1, cascadeDelete: true)
.Index(t => t.ParentID)
.Index(t => t.ParentID1);
where two columns are created for course but i don't want two columns(t.ParentID and t.ParentID1), I want only ParentID where i will insert student and employee id's .
Can anyone guide me to fix the above or any suggestion to implement the above scenario ?
I am using EF 6.0 version.