When being interviewed as the Best student, you should keep a few points in mind-
I) firstly most importantly, you need to sound modest and simple, it will cast a very bad impression if you are proud and showy.
ii) Next, it is also necessary to praise other students as well, Use phrases like-'' I'm really honored to emerge as the best student among a lot of such talented students'' or " In our class we have many excellent students, they are not at all less talented than me, this was just my year".
iii) Never ever forget to thank you teachers, mention their names too.
iv) Also you must thank your parents for their support and help.
v) Lastly you must give some good study suggestions to the coming batch as well, be encouraging too.