Teachers can find your child's potential very fast. They have been teaching many children for so many years, who is different from the others is easy for them to recognize. If you don't ask, they wouldn't mind. They want to keep good students in their school. And also if you meet a very good teacher, your child may get many extra work from the teacher. Another thing I may want to mention is before let your child for the test. Ask him or her if he or she likes or not, their feeling is very important, ask them " do you want to keep in the present school to be the top student, or do you want more challenges, you have to work very very hard but may still not top in the class."