C# - Custom Control's Controls.Count Zero?

In a custom server control, I am simply writing out the number of child controls.

Is there a reason that the count would go to zero if <% %> tags are used within the body of the control tags?

Here's my extremely simplified control:

public class Script : Control
{
public override void RenderControl(HtmlTextWriter writer)
{
writer.Write(this.Controls.Count.ToString());
}
}

When passed only Literal data, the count written is 1 as expected:

<my:Script runat="server" ID="script3" >
function foo(){}
</my:Script>

When passed Literal data and some computed data, the count goes to zero:

<my:Script ID="Script1" runat="server" >
function foot(){}
<%=String.Empty %>
</my:Script>

There's nothing special about the String.Empty either. Anything I put here results in a count of zero.

Interestingly enough, other Control tags work fine however. The following counts 3:

<my:Script runat="server" ID="Script2">
<asp:HyperLink runat="server" NavigateUrl="/" Text="hi" />
</my:Script>

Is there another way to get the child "content" of the custom control? I would think there is some way, as does it, but I can only inspect the metadata for System.Web.UI.WebControls.Content - not the implementation.