I doubt they'll throw you out of the school for having a "tacticool pack" but you will probably be socially ostracized for it. Like that weird kid who goes to school with camo BDU pants, army boots and a mullet. You are not doing yourself any favors. The Japanese have a saying... The nail that sticks out gets hammered. There is not benefit to standing out. My advice; get a standard book/laptop bag from the usual suspects.
The whole dual purpose reasoning that it's for school and outdoors stuff is false by the way. There is nothing about tacticool packs that makes them superior to standard bags for outdoor use. In many ways they are worse. They weigh more and generally have poor hip belts. All that counts in a hiking pack is that the suspension system is good and that you can fit your stuff in it. That second part is worth considering since if you can fit your camping gear into a school bag it means either your school bag is waaay too big or you have an admirably compact camping setup.
tl;dr Get a normal bag for school
The whole dual purpose reasoning that it's for school and outdoors stuff is false by the way. There is nothing about tacticool packs that makes them superior to standard bags for outdoor use. In many ways they are worse. They weigh more and generally have poor hip belts. All that counts in a hiking pack is that the suspension system is good and that you can fit your stuff in it. That second part is worth considering since if you can fit your camping gear into a school bag it means either your school bag is waaay too big or you have an admirably compact camping setup.
tl;dr Get a normal bag for school