Bobby has always struggled Academically, but it was impossible for Xavier to ignore his desire to assist in operations of the facility.
Bobby is one of the more powerful mutants, and one of the few people who have managed to underestimate his own abilities. In a more dedicated mindset, he could be one of the most powerful mutants in the world.
Bobby has a carefree attitude that reduces stress in the faculty. Xavier finds some students enjoy his personality and find him trustworthy. He is also quite capable of keeping his students safe.