You can disable the tools on a per-user basis, or for all users. You just need modify the access-rights for the programs in the C:\Windows\System32 folder.
- Magnify.exe
- Narrator.exe
- Osk.exe
To prevent a user from executing a file:
- Make yourself owner of the file.
- Open Properties dialog for the file.
- Select the Security tab.
- Click the Advanced button.
- Select the Owner tab.
- Click the Edit button.
- Select yourself in the list.
- Click the OK button.
- Close all the dialogs. (To update for the new owner)
- Make the user unable to execute the file.
- Open Properties dialogs for the file.
- Select the Security tab.
- Click the Advanced button.
- Select the Permissions tab. (Default)
- Click the Change permissions button.
- Click the Add button.
- Type the username, or find by clicking the Advanced button.
- Alternatively, you could add Users for to disable them for everybody.
- On the row Traverse folder / execute file and row Deny, check the check-box.
- Click the OK button.
- Close all dialogs.
Now the keyboard-shortcuts won't do anything. At least not anything visible.