First Coast High School

I'm looking for a program of distance education for the additional courses that do not cost more than $ 500.

I know about:
Penn Foster
Continental Academy
First Coast Academy
Citizens
Keystone
Compuhigh

are not there any other line with secondary schools rule?

Take a look at K12.com and see if they offer virtual academy in your state, and if they do, see if it includes the high school. They are free, if it is available where you live.

Edit: In my state (Ohio), they offer courses in high school. In some states, they only K-8.

There are many universities that offer programs for high school diploma by distance learning (correspondence and online). They are often cheaper online High School "Business" and they are 100% legitimate.

Three that I know are now (I am doing research to discover more of these):

Indiana University (diploma + level)
Harvard University (classes, but no HS diploma, AA possible)
The University of Missouri (diploma + level)

I think all three also offer options for dual credit (high school and earn college credit at the same time).

Affordability I'm not sure how to interpret your text. If you mean $ 500 per year, all over your budget. If you mean $ 500 per course, the sole of your budget is Harvard. If you mean $ 500 per semester, IU and MU are within this budget.

The first link below will take you to all three.

*** You can also watch the MIT OpenCourseWare (free), but does not provide credit / diploma (2nd link)

I agree with darcy34 but K12 is only the fifth year, I think, but check it good luck looking for the same thing

Try this link and see the many options to explore.
http://www.google.com/search?q=online+ho ...

I do not know where you live, but here in British Columbia (Canada) certain online programs for high school are free. Only international students pay, but you can ask.
Here's the link: http://www.surreyconnect.sd36.bc.ca/Page ...