Head to Admin > Census and on the right side of your screen under View Your Census Summary click on 'Official School Summary - HTML Only'. This will open up your census summary in a new tab. Right click on this page, and click on Save As and this table with pop up:
Save the summary as HTML and select where you wish the file to be saved to. It will default to your computer Downloads folder. You can then select this file when sending in a secure email.