Our school uses the OLSAT for G&T screening, and the score they use to determine whether you met the cutoff is [actual score + standard error of measurement]. SEM when my DD took it was a bit more than 5, and our school uses a cutoff of 128. So in our district, she'd qualify for G&T services based on that score.

If your district requires qualifying scores in both OLSAT and achievement testing, that would account for the low percentage being screened in.