You got to use the right glove for the right task
No, there a school. They have every right to demand certain standards for equipment used by there students. Some use branded gear as well as branded uniforms, in which case you got to buy it from the school. You don't join a hockey team and demand to wear your own jersey and colours. They can make whatever uniform and equipment requirements they want.
People buying gear elsewhere just means the school gets less in equipment sales and will have to make up that difference in some other way (ex higher tuition)
I can understand making money as a business, but I think they should upgrade their equipment standards to something that's at least decent. Buying specific uniform is one thing, but decent gear meant to protect students is different.