I've been researching old newspapers and found the following article in The Texas Sun, published in Richmond, Texas on July 28, 1855. (Click here to read the complete newspaper at The Portal to Texas History, an excellent Web site by the way.)
The Handbook of Texas says the academy was in operation in 1850, but closed due to bankruptcy in 1858. At its peak it had 3 instructors teaching 70 white students. You can see from the newspaper ad the subjects they studied. Prices seem reasonable at first glance, but people didn't make much money back in those days.