Where in Houston, can I gain experience working with children and people who have developmental disabilities?

Hello everyone, I have a BA in Psychology and I worked one year as a Psychiatric Nursing assistant (inpatient, jail diversion with acute adults). I want to gain experience working children and people who have developmental disabilities. I live in Houston and I've looked online at Google, Indeed, and volunteer sites. I couldn't find where I can volunteer or work to gain experience without having experience working with this population.