I don't know about blocking one IP from your primary site but allowing it for an add-on site, using .htaccess. That might get complicated. I'm not familiar enough with the innards of WordPress to say exactly how to do it, but it might be possible to look at the IP address used for access, inside your family site, and reject it just for that site. WP might even have IP blocking built in. Mitch?

When you say that some students are "too interested" in your family site, are they getting in and reading/posting, or are they successfully hacking it? Don't you have user IDs and passwords to control access to your family site? I thought WP had such. If not, consider moving your family site down one level to a subdirectory, and password-protecting that directory, or maybe implementing IP blocking on that directory. Or, if your family site is being actually hacked, it sounds like you've got some security issues somewhere.

Actually, if you search online on how to do this, you get a great guide on wordpress itself:

http://codex.wordpress.org/Combating_Comment_Spam/Denying_Access

The issue with most of the methods listed is that your family site is the main domain and .htaccess entries blocking an IP will apply to all sub and addon domains inside public_html so you have to use a method that won't block the class page. The best one listed there for doing that would be the bottom one where they mention putting this code at the top of any page you don't want them to access:

<?php
$block = array("xxx.xxx.xxx.xxx", "yy.yy.y.yyy");

if (in_array ($_SERVER['REMOTE_ADDR'], $block)) {
    header("Location: http://google.com/");
    exit();
}
?>

Probably putting it into the index page for your family site would do the trick. You'd have to replace the "xxx.xxx.xxx.xxx" part with the actual IP you want to block.

If this is a family site and you do not want people other than your family viewing it, why allow access to anyone at all anyway? Why not just allow only family members to view it by password protecting it? Having it online without password protection means you have it getting searched by search engine spiders and linked in their indexes for other people to find. The only way to prevent access to people would be password protection in the long run.

btw - I did a temporary thing for the day...

I blocked the wp-content folder of wordpress for just the school's IP. When accessing my family site you get unformatted text because it can't access the theme file. Class page works fine.

I like the idea of putting a header in my family page to block specific IPs. Hopefully I only need to do this on occassion. I should have it redirect to NSA.gov or someething.  Anyone have a good scary but safe for school site to redirect to?

Great, glad it worked for you

Redirect them to here to the scariest site I know!