BTDT parent experience. If the dad and you have disagreements, then this becomes matrimonial law/ special education law hybrid. One parent needs medical and educational final say. ADHD is a medical diagnosis that can adversely affect education. Districts only recognize the custodial parent that has educational custody.
There is no right person to render an opinion. You will need your expert witness and the dad will have his. Could be any expert, such MD, PsyD, PhD, teacher, social worker. It would be best to have 2e input, but the court is not going to require it. Also depends on who your judge/referee is. If you get a 60+yo that was never involved with his/her DC, then he/she will probably not have a good understanding of IDEA.
Feel free to PM me if you need to discuss further.
