Look, I wasn't taught any of this either, and I went to school in Massachusetts (Yankee as heck.)

But search the web for: Texas Revolution Slavery or Texas Cotton Slavery

There are sound arguments from historians that slavery was indeed a significant factor in the Texas Revolution. Was it the only factor? No. But it was significant. In those days, in cotton land, cotton was not economically viable without human slavery. I also didn't know that Texas was cotton land back then.

The Texas Convention of 1836 explicitly legalized slavery.

I was never taught any of that. However, as I said in another comment: "But I get it, it's nicer to wrap up history in a nice bow when teaching children."

I am on the old side of age, and I have to say that it's nice to still be learning things. Maybe the Internet wasn't a mistake :)

edit: BTW, my deceased father's Cameron (Iron Works) and Cooper Oil Tools coveralls are hanging about 20 feet from me. I am not unfamiliar with modern Texas.