I've taken 4 different "ground schools" all of them had faults. I expected as much since I was taking the training based on a Rule that doesn't go into effect until August 29. I found the Drone Pilot School to be really well done. Lots of presentations. Could I have found this stuff elsewhere on my own? Sure. Not sure I would find it all in one place. Won't do you any good just studying 107 because you also need to know a lot or "private pilot" stuff as well.
While Alan is the face of the school and the one actually delivering the material he said that in an email: "The course is taught online, and entirely self-paced, meaning you can go through it at your own pace. Our instructor, Dennis O’Hara, has a 20-year career in aviation and education." I've had a lot of interaction with Alan and none with Dennis. I completed the course. As a bonus, he has you do a flight test, nothing overly complicated (and not really required by the FAA) and he also has a presentation by a "drone lawyer" which was interesting. This was the second "ground school" that I took and by far the best of the four) Alan is very responsive to questions. Because I had taken a previous course, I believe my discount was to around $219.
I'm also using the Android App Dauntless Ground School for Remote Pilots. Nice to have it on my phone and I can take a practice test anywhere anytime. Does a great job of explaining the test question and you can set that information for only the one's you get wrong or for all of them. This was about $40.
Also signed up with ASA's Prepware Online. Basically another online practice exam site. I believe this was $40.
The forth one ( the one I actually took first) was CTI "Exam Prep for FAA Small Unmanned Aerial Systems (sUAS) Test. This one had some great information but was already out of date by the time I took it. It looks like they have updated part of the course since I've taken it. It looks like the original course I took was based on the first draft 107 that from around Feb. If I remember correctly it had a different altitude limit than what is currently going into affect. The instruction was delivered by an actual pilot and he was really good. I did learn a trick or two. I believe this was $80.
I've also read over material collected by Sara Nilsson. She has done an interesting job of putting together a free training site in about 9 modules. See
Sarah Nilsson - UAG Test Prep - 1.
Did I need to take all of these courses? No. But I tend to do over information and all of this was interesting. I think just as important (perhaps even more so) is to practice flying. I like to fly with GPS for a nice stable platform but I also practice with it in Atti.