You don't have to pretend that you're considering the public schools to get testing done. In fact, it is advisable not to do so, as if and when that info comes to light, it will add unnecessary animosity to your relationship with the district. Public schools are responsible for child find of all students who are resident in their district. I have evaluated many a child who was not enrolled in ps, and where the family had no intention of doing so. What you do have to give is a plausible referral question that involves special education. Where there is no gifted mandate in Mass, that will require some area of possible disability.
You can request testing through the schools once a year, but they may decline to do new cognitive testing, if it's been under two years, on the grounds that the old cog is still good. I usually try to avoid that kind of over testing, unless there is reason to believe it was not valid. Mass still has the discrepancy model on the books, so you can say, quite honestly, that you are concerned that your child may be 2e, so even though he has some decent academic skills, you worry that he may be underperforming in some areas. That will put the gifted question on the table, but still allow for a legitimate special ed referral.
