Can Not Select other Years in DropDownList

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ASP.NET

Hello. I have three DropDownList on a form. One is school names and the other two are years. I have the DropDownList that are years to populate two textboxes when a year is selected. I also have all three DropDownList databound. The year DropDownList has populated with all the years from my database. I was trying to get it to only populate with the years that match the school. Next what I am trying to do is to select a school's year from DropDownList year to populate the textboxes. The population works but when I select a different year it resets back to the first year that was selected. What am I doing wrong? Can someone help me?!!!

protected void DropDownListSchools_SelectedIndexChanged(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["PasswordConnectionString"].ConnectionString);
        con.Open();

        lblINST_ID.Text = DropDownListSchools.SelectedValue;




    }
    protected void DropDownListCFY1_SelectedIndexChanged(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["PasswordConnectionString"].ConnectionString);
        con.Open();
        SqlCommand scmd = new SqlCommand("Select TOTASSETS, TOTLIABILITY from TableFIN where INST_ID = " + DropDownListCFY1.SelectedValue.ToString(), con);
       
        SqlDataReader dr = scmd.ExecuteReader();
        if (dr.Read())
        {
            TextBoxTA1.Text = dr["TOTASSETS"].ToString();

            TextBoxTL1.Text = dr["TOTLIABILITY"].ToString();

            

        }
        dr.Close();
        con.Close();
    }
    protected void DropDownListCFY2_SelectedIndexChanged(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["PasswordConnectionString"].ConnectionString);
        con.Open();
        SqlCommand scmd = new SqlCommand("Select TOTASSETS, TOTLIABILITY from TableFIN where INST_ID = " + DropDownListCFY2.SelectedValue.ToString(), con);

        SqlDataReader dr = scmd.ExecuteReader();
        if (dr.Read())
        {
            TextBoxTA2.Text = dr["TOTASSETS"].ToString();
            TextBoxTL2.Text = dr["TOTLIABILITY"].ToString();

            

        }
        dr.Close();
        con.Close();