The answer is using the ‘RegisterClientScriptInclude’, I think it is not possible natively to add script to the <head> element. However there is an alternate method using the System.Web.UI.HtmlControls.HtmlGenericControl class as shown below:
protected void Page_Load(object sender, EventArgs e)
HtmlGenericControl ctrl = new HtmlGenericControl("script");
Run the application, right click the page and View Source.
As you can see, the script is now registered in the <head> instead of the <body>.