K.A.
No, it will not affect his school record, and if he is just behind in speech development and no other problems he is not considered a disability child. My son was also behind in speech, my doctor had it documented, but never mentioned it to me until after he started school and the school informed me. I wish I had known early enough to have him worked with prior to starting school. We ended up having to hold him back one year of school that could have been avoided if my doctor had told me ahead of time that he need therapy. He is now in 3rd grade, doing normal studies and making average grades and better. If the doctor recommend therapy now, do it and maybe you can avoid the frustration later that I had to deal with.