I'm not really sure what you have to do to be certified in ABA but working as a TA for a special needs program might be an easier position to obtain! I have heard from many people who have worked in this field and then be successful in getting into schools. Plus it's a great way to not only observe speech sessions, but a variety of it as well. For ex. the program that I worked in has many classrooms so the cognitive levels of the students were all very diff, so I was able to see speech sessions ranging from solely relying on aac devices, to how to socially interact w peers, to motor control issues, and I feel like that gave me a great foundation for speech