This makes absolutely no sense to me. Please Help. (before I go postal)

This code gives me two records: 

SqlConnection cn = new SqlConnection(ConfigurationManager.ConnectionStrings["simsConnectionString"].ConnectionString);
cn.Open();
SqlCommand cmd = new SqlCommand("SELECT c.ID, c.ClassName FROM Class AS c INNER JOIN TeacherClass as t ON c.ID = t.ClassID WHERE t.TeacherID = " + intTeacherID, cn);
SqlDataReader dr = cmd.ExecuteReader();

which are:

 Then I assign the values from the SQLDataReader to a List<classes>

Code for the Class classes:

public class classes
{
     public int id = 0;
     public string name = "";
}

Code for the assignment:

List<classes> cls = new List<classes>();
classes classdata = new classes();
while (dr.Read())
{
     classdata.id = 0;
     classdata.name = null;
     classdata.id = Convert.ToInt32( dr[0].ToString());
     classdata.name = dr[1].ToString();
     cls.Add(classdata);
}

I end up with two instances of ID=54 and name = Form 1 C in cls. Why?

Please help.