How can I relearn high school subjects?

https://www.khanacademy.org/ has math and science curriculum. Looks like they've got math up through Calculus, and they do have some Physics as well. They've got relationships set up between different units, so you can see what the prerequisite knowledge for something is, and what it leads to. Sounds like a great fit for what you're looking to learn!

Oh. Well if you're trying to prep for a specific test, test prep is going to get you a lot further than general knowledge well. Buy the kaplan books and work through those.

I know that a lot of the states, including http://zsem.k12.com/tpages/desks_allhs.html?gclid=CP_Fh-Lf5rYCFVQFMgod_nkAkQ&st=GA&leadsource=sem&product_type=va&product_interest=gca&target_audience=gen&target_grade=hs&utm_campaign=Georgia_Local_-_Diploma_Desktop&utm_medium=sem&utm_source=google&utm_term=on_line_highschool_diploma&adgroup=High_School_Diploma_Online&keyword_match=broad&message_class=direct_response&vendor=ef&provider=google&geo_distro=ga&ef_id=UXlAGgAAALT1Nhu0:20130425212018:s, have http://national.connectionsacademy.com/SummerSchool?utm_source=google&utm_medium=cpc&utm_campaign=National_-_Summer_School&adgroup=z_-_Summer_High_School&keyword=online%20high%20school%20summer%20courses&matchtype=b&creative=31212149744. But I've really got to wonder why you'd want to do this. Certainly, you can refresh your existing foundational knowledge by obtaining some cheap textbooks and going over the material again. But unless you have a practical reason for wanting this information and a way of USING it in life going forward, you're likely to forget it again. I find that you can sit through classes and get excellent grades in them, but if you don't use what you've learned in a real-life application, that the information just gets shuffled to the back of your brain. Why do you want this information now? What will you do with it? Perhaps you might do better reading intersting books about the topics you wish to study. For example: Algebra--http://www.amazon.com/exec/obidos/ASIN/0965911381/metafilter-20/ref=nosim/ Biology--http://www.amazon.com/exec/obidos/ASIN/1400052181/metafilter-20/ref=nosim/. Chemistry--http://www.amazon.com/exec/obidos/ASIN/1613744528/metafilter-20/ref=nosim/ Basic Mechanics--http://www.amazon.com/exec/obidos/ASIN/0061673730/metafilter-20/ref=nosim/ Physics--http://www.amazon.com/exec/obidos/ASIN/046502811X/metafilter-20/ref=nosim/ I find that reading good non-fiction books about stuff that interests me is WAY better than going back to high school.

Taking algebra test, study algebra. Taking ASVAB test, study ASVAB.

I'm pretty sure by "basic mechanics" is meant "Newtonian physics of objects in motion", not motorcycle repair. Seems to me you just need to visit your local public library.

iTunes U has numerous open source courses and materials that would fit your needs.

Typically undergrad 101 type classes have "the" book that a lot of schools use. For biology, it's Campbell's Biology, for example. Find the book for these 4 topics and supplement with the internet, especially Khan.

Bonus: "the" book usually has a billion editions and older ones are available for like $5 on Amazon.

But I've really got to wonder why you'd want to do this. I'm taking the ASVAB in the fall, and want to kick its ass.