David_G

Contact your host for assistance if you need help with cloning.

For what you are wanting to do, membership is the easiest way. Once it’s setup it’s easy. Here is a better plugin for what you are asking and this one is up to date. https://wordpress.org/plugins/contexture-page-security/

The plugin that #santeven suggested looks like a good option for what you want. The students will have to be logged in to your WP site, but with that plugin you set the permissions for what your users can and cannot do. It will take a little work to set it up. You can create “ROLES” for your users, then go from there. As far as keeping your site off google, make sure you checkmark “DISCOURAGE SEARCH ENGINES” in SETTINGS > READING. You can also add a robots.txt file in the root of you site to further discourage search engines from indexing your site.

If you make a mistake with your functions.php file your site will likely go down, If you do it in a child theme, then all you need to do is rename the funtions file in your child theme to something else by FTP and your site will come back online, then you can figure out any mistakes.

The best way to make changes like this to a theme is to use a child theme, so your tweaks won’t be overwritten when updating the theme. Here are some guides in case you haven’t made one before:
https://codex.wordpress.org/Child_Themes
http://op111.net/53/
http://vimeo.com/39023468

You should also check this out for customizing your site.
http://themesandco.com/snippet/firebug-best-spent-6-minutes/
http://getfirebug.com

Then to edit this editor is fantastic. You can edit multiple files at the same time.
http://notepad-plus-plus.org/

And this FTP program is tops in my book.
http://www.coreftp.com/

Try this in your custom css.

#masthead {
display: none;
}

@santeven, I agree with you for minor modifications, but even a beginner needs to know WHAT to style, hence my post about firebug and how to use it, and you must agree that the BEST way to customize is by child theme so I provide information on that. If you don’t have the tools, you can’t use them.