Type in GED into a search engine and watch all the ads that appear. Click on some of the ads and you will see that most are going to charge people to study or take a test to get a sometimes dubious credential.
My name is Brett Taylor and I am employed by Pinellas County Schools (Florida) to teach an online GED preparation class. In the year I've been doing this I have run into many students who paid some of these "diploma mills" to obtain a credential that proved worthless.
There are two main ways to obtain a high school diploma, by completing credits or by passing the GED Tests. Some online schools offer credits; some prepare you to pass the GED Tests. The actual GED Tests are only given in person and never online.
Online High Schools offering credits vary from reputable to total scams. The reputable ones typically require a copy of your high school transcript, which they evaluate and then determine what courses, if any you need to take. Many students already have enough credits to graduate but live in states where students are required to pass a test (like the FCAT in Florida) before they are given a diploma. An online high school based in another state, like Maine, can grant a State of Maine diploma to such a student because they are an accredited high school in Maine. Before paying anything I advise you print out information from the school and take it to the place you plan on using it (military recruiter, employer, or school).
Scam sites issue an high school diploma based on "life experience". Typically you take an entrance test online. If you don't pass the first time, you can try again. The second time the correct answers might be shown in red, click on them and at the end you're told congratulations, you passed, now send us the money and we will send your diploma. Don't get fooled by claims of "accreditation". If you are not familiar with the "REAL" accrediting associations ( like SACS) you could be fooled. Anyone can claim to be accredited and prove it by creating their own accrediting association and approving their own school.
My class is for students who live in Pinellas County. My students all start by taking a TABE test in person. based on those results I design a course of study for them using password protected commercial online programs, if they need to study. Many students already have sufficient knowledge and skills to pass the GED Tests so I simply assist them with that process and sign them up to take the GED Tests.
There is no charge to students except the $70 fee for taking the GED Tests and there are scholarship opportunities to cover that fee.
I have also compiled a list of free online resources that can be used by anyone in any state or country to study. Additionally I have recordings of past live online classes I taught available for free on topics such as Fractions, Percents, and Negative Numbers. My website to find all these resources as well as contact information and information about the GED is listed in the signature.