Hi, I'm a BCBA so I'll try to explain an FBA the best I can. FBA stands for Functional Behavior Assessment. It's based on observations, questionnaires from people who know the individual, and anecdotal information. An FA is a Functional Analysis where you create analog conditions to test and control behavior to determine function. An FBA is usually sufficient to determine the function of the behavior. Both an FA and FBA are going to give the function of the behavior as attention, escape, access, automatic. It sounds like you don't think the function is escape (he just really doesn't like them so he refuses to go to school when he knows they're going to assess). Sounds like you think perhaps it's some other reason? Take anxiety as an example. As a BCBA, I can't work on things like anxiety because it isn't a function of behavior and I also cannot measure it (I can't count it, I can't record how long it happens, etc. It's a feeling, not a behavior.) That's not to say people don't experience anxiety, but that isn't a function of behavior. So if I had a client in this situation who I assessed as school refusal is escape maintained behavior, and after talking with the parent and learning "Billy" has a lot of anxiety about assessments, I could do a bunch of different approaches to address it like giving him a list of activities we would do during the assessment so he knows before hand, pairing myself with reinforcement with him so he's not nervous about a new person, etc. Does this help?