So kingdom is quite evil. Enlisting children. MC is not interesting and stupid. You would assume that person who, all his life lived through rational thinking (at least that what we see), would think that trying out hero course with his abilities would be serious detriment. Using his powers would be bigger detriment. Now, alone destroying instructors magical weapon? He is straight out retard.
How his missions were success when he doesn't do any recon? Only support is miles away and MC is lost in a city unable to ask directions.
I mean, usual manga like this, shows stupidity after 7th to 10th chapter or so. This one went full retard on 2nd. This manga is definitely at best 5 (average).