@Zergio200ism You forget that the world he is currently in is that of a medieval monarchy with magic on the side. Status and blood lineage are everything in these settings, and if you are an orphan on the street, the nobility can do whatever they want to you and you have no right to complain. Especially since, even if he can use a little bit of magic, he is:
1.) Still a child, not even a teenager yet and unable to deal with the numerous physically stronger adults that know how to use magic.
2.) Already being suspected for the kidnapping case with the princess where, even if he's innocent, there are already people willing to get rid of him to save and raise their own political position.
3.) Unable to use his magic properly at all, which attending that school can fix. However,
4.) If he talks back to the royals, considering the above 3 points, he will be kicked out of the school that can teach him how to use his abilities and killed.
In the end, he's making the smart decision as a person with too little power, too little influence, and zero backing in an environment where your bloodline and you household are the most important things before anything else. Had he followed what you suggested, the story would end with his death.