You say you are wanting a local batch script to do nothing but NET USE a network share as S:\, then run a remote batch script, e.g., S:\test\test.bat, and you want the local batch script to run every time on system startup?
The share mapping part is actually done for you by the NET USE command - type the following once to have S: available as a mapped drive from now on:
NET USE S: \\server\share /PERSISTENT:YES
Mapped drive S: will be available from now on at startup, without running any other batch script: immediately run your S:\test\test.bat.
To run this batch script - or any other executable - at startup, right-click the script/executable, and drag it to Start Menu, All Programs, Startup folder, and drop it (not on the folder, but in the expanded space just below it where other startup programs are): because you right-clicked, Windows Explorer will prompt you to "Copy here", "Move here", or "Create shortcut here" for the file. Select "Create shortcut here" - the file will run at startup from now on.