Although there were many casualties, in the end, they were not as many as a classic raid would have caused. All the cadets survived, as did most of the Mecha officers; really, the bulk of casualties were among the soldiers who did not have autonomous fighters. The mission itself could be considered a success.
It is true that the sector had not been recovered; the arrival of reinforcements meant that it was still occupied by the enemy, but what could have ended in tragedy was, in the end, a resounding victory.