Psychic Academy Oura Banshou

From Tokyopop:

Zerodaimu Kyupura Pa Azalraku Vairu Rua Darogu (a.k.a. Zero) once stopped the evil demon lord with his incredible psychic ability, and in the process saved the world from destruction and earned the honorable and highly imaginative title 'The Man Who Stopped the Evil Lord.'

Now, he has accepted a position as a teacher at Psychic Academy, a school for gifted psychokinetic youngsters who have demonstrated incredible raw powers and want to learn how to hone their abilities. Among the student body is young Ai Shiomi, Zero's little brother, a somewhat meek boy who, despite parental prodding and his fraternal reputation, feels that his limited skills hardly justify his presence at the prestigious academy.

However, everyone else is convinced that he, like his celebrated brother, is destined for greatness. A lot of pressure for a boy just entering adolescence!