I forgot the code

Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load

If Not Me.IsPostBack Then

ddlDre.DataSource = dsDre
ddlDre.DataValueField = "Id_Dre"
ddlDre.DataTextField = "Nome"
ddlDre.DataBind()
ddlDre.Items.Insert(0, New ListItem("SELECIONE UMA DRE ...", ""))

Else

'PopulateCheckedValues()

'SaveCheckedValues()
'PopulateCheckedValues()

End If

End Sub

Protected Sub OnRowDataBound(sender As Object, e As GridViewRowEventArgs)

If e.Row.RowType = DataControlRowType.DataRow Then
e.Row.Attributes("onmouseover") = "MouseOver(this);"
e.Row.Attributes("onmouseleave") = "MouseLeave(this);"
End If

PopulateCheckedValues()

End Sub
Protected Sub gdvEscolas_PageIndexChanging(ByVal sender As Object, ByVal e As GridViewPageEventArgs)

SaveCheckedValues()
gdvEscolas.PageIndex = e.NewPageIndex
ListarEscola()
'PopulateCheckedValues()

End Sub

Private Sub PopulateCheckedValues()

Dim userdetails As ArrayList = CType(ViewState("CHECKED_ITEMS"), ArrayList)

If userdetails IsNot Nothing AndAlso userdetails.Count > 0 Then

For Each gvrow As GridViewRow In gdvEscolas.Rows
Dim index As Integer = CInt(gdvEscolas.DataKeys(gvrow.RowIndex).Value)

If userdetails.Contains(index) Then
Dim myCheckBox As CheckBox = CType(gvrow.FindControl("chkEscola"), CheckBox)
myCheckBox.Checked = True
End If
Next
End If
End Sub

Private Sub SaveCheckedValues()

Dim userdetails As ArrayList = New ArrayList()

Dim index As Integer = -1

For Each gvrow As GridViewRow In gdvEscolas.Rows
index = CInt(gdvEscolas.DataKeys(gvrow.RowIndex).Value)
Dim result As Boolean = (CType(gvrow.FindControl("chkEscola"), CheckBox)).Checked
If ViewState("CHECKED_ITEMS") IsNot Nothing Then userdetails = CType(ViewState("CHECKED_ITEMS"), ArrayList)

If result Then
If Not userdetails.Contains(index) Then userdetails.Add(index)
Else
userdetails.Remove(index)
End If
Next

If userdetails IsNot Nothing AndAlso userdetails.Count > 0 Then ViewState("CHECKED_ITEMS") = userdetails

End Sub

Sub Inserir_Supervisor_Escola()

Dim conexao As SqlConnection
Dim cmd As SqlCommand
Dim sql As String

SaveCheckedValues()
gdvEscolas.AllowPaging = False
ListarEscola()

For Each row2 As GridViewRow In gdvSupervisores.Rows

Dim checkbox As CheckBox = CType(row2.FindControl("chk"), CheckBox)

For Each row As GridViewRow In gdvEscolas.Rows

Dim checkbox2 As CheckBox = CType(row.FindControl("chkEscola"), CheckBox)

If checkbox.Checked And checkbox2.Checked Then

sql = "Insert Into pr_Supervisor_Escola (Matricula, Id_Escola, Id_Dre, DataCadastro, CadastradoPor) values (" & gdvSupervisores.Rows(row2.RowIndex).Cells(3).Text & ", " & gdvEscolas.Rows(row.RowIndex).Cells(1).Text & ", '" & ddlDre.SelectedValue & "', '" & Date.Now & "', '" & User.Identity.Name & "')"

Try

conexao = New SqlConnection(strConn)

conexao.Open()

cmd = New SqlCommand(sql, conexao)

cmd.ExecuteNonQuery()

conexao.Close()

gdvEscolas.UseAccessibleHeader = True
gdvEscolas.HeaderRow.TableSection = TableRowSection.TableHeader

pnlMensagemErro.Visible = False

pnlMensagemSucesso.Visible = True

Catch

pnlMensagemErro.Visible = True
lblMensagemErro.Visible = True

lblMensagemErro.Text = "Ocorreu um erro!" + Err.Description


End Try

End If

Next


Next row2

End Sub