I would not wait and let your child lose a school year to this. I did this and my son never recovered from the loss , meaning he never caught up or forgave me for making him graduate a year later than all the other kids who were in classes with him early on as they made fun of him for falling behind all through his academic career. We have lived in the same community all his life. On the other hand his sister skipped a grade and never caught up by learning all the things she missed in the grade she skipped (fractions). Consequently she had great difficulty with math and english(creative thinking).
Just do everything in your power to get them through each grade sucessfully. You are your childs only advocate. His only knight in shining armor. stick up for him and get him what he needs when he needs it.
P.S. I also never put him on medication in his elementary years and i should have . once he got on medication in the 11th grade he excelled with a 4.0 grade point average up from a 1.5
You may want to be more aggressive in terms of getting him into a psychiatrist's office, since it seems that you are thinking re medication for the mood swings. A little pressure on the school may help, or circumventing the school and finding a private psychiatrist might be in order.