I have mixed feelings about using a test like the OLSAT for entry into a G/T program. On the one hand, how should entry be decided? Teacher recommendation? We've all seen teachers who didn't "get" our kids, so that doesn't seem quite fair. Parent recommendation? Again, although we are most qualified to judge our kids, that seems a bit odd too.
A closed book exam like the Cogat, OLSAT, whatever? That is probably the fairest, yet what if your child just has a bad testing day. Etc.