Make sure it's integrated, modular is way too long.
Absolute nonsense. Check out CAE Oxford Aviation Academy and you will find out that the modular ground course is exactly as long as the ground school of the integrated course. But if you've done your research properly you should know this... I believe it's the same for other schools as well.
I'm a modular ground school student at OAA now, and it's all just top notch! Instructors are very friendly and very good, with lots of experience in aviation. I came straight out of school from my home country, and find that the ATPLs for me are a huge gap from PPL to ATPL. That said, English isn't my first language so sometimes I've struggled a bit with complicated words.
Good luck whatever you do, and make sure you do proper research!
