When ATA was founded in 1969, GM H. U. Lee was teaching the Chang-Hon style of ITF. He began to develop his own style in the early 80's and presented the first three forms of the Songahm style at the ATA instructor camp in 1983.
When GM H. U. Lee passed away from cancer in 2000, GM Soon Ho Lee became the second presiding Grandmaster of the organization. He's since retired as the presiding Grandmaster, but is still very active in ATA.
I don't believe that Tiger Rock is an ATA school. Since you live in Kingwood, you might check out Henderson's ATA. I've known Master Henderson for many years and highly recommend him.
Edited to add: the individuals I showed are my direct lineage. However, there are numerous senior ranks in ATA that I have trained with, and I consider them my instructors as well. I try to learn as much as I can from as many people as I can.
Thank you for the information, you have been very helpful. It is still a good drive, but I plan to check out Henderson's today. My grandson is very happy at Tiger Rock, that's the most important thing for now. My first school was MDK in 1973, so the forms my grandson is learning is very different from the ones I know. I want to learn the same forms as my grandson so I can help him, but I would like to go to a school that taught better balance and precision. I hope Henderson is the place I am looking for.