There are TONS of good videos on YouTube. I realize that watching a video is NOT the same as having a live instructor watching and correcting you. However, I have learned a lot from them. I find that every time I go ride after watching them, I am more intentional about putting into practice what they cover, and it does have a positive impact on my riding. It's also free.
That said, I have done a class, and I really liked it. I think the big benefit of the class is the immediacy between the lesson and the practice. It is also just fun to be doing it with other folks. I'd love to do one of the tour style packages with RawHyde or Jimmy Lewis where they actually take the class out on a trip for several days to a week.
As Jarrett mentions, if you can find some other riders that are skilled and experienced, riding with them can do wonders for you, unless they ride real fast and suck you in over your head... I have seen that happen too many times! The good experienced riders will watch and respond to less experienced riders, coaching and helping, rather than trying to show off and impress. I have been fortunate in this regard and have ridden with some great folks.
Unfortunately, there are not many formal options in Texas. Most of the stuff seems to be focused on the Rockies and the West Coast. Bill Dragoo in Oklahoma is the closest school I know of. Here is the one I did,
http://www.adventureridersinternational.com/schools.html
They will come to any location if you get enough people together. The key is to have a good location that offers a nice variety of terrain. That will really determine just what skills you can learn. I did some work for them in exchange for doing their mid and expert level classes. Lorne is the lead instructor and is very good. I spent the first day observing the beginner class, shooting video and taking pictures. The students seemed to really engage with him and enjoy themselves. It was amazing how quickly some of the students improved just from the morning through the end of the day.
I think some of the other classes will come to a local location if you get enough people to commit. You'd have to call and check with them of course. Some even bring smaller bikes so you can practice a skill on the small bike before attempting it on a bigger adventure bike. Lorne had a nice old XR 400 that he let folks use.