The header is a part of WordPress theme which will be loaded every time a WordPress page is loaded, so if you insert schema in the header part, the schema will be loaded every time.
LOCAL BUSINESS Schema for a master domain site (the type of sites we teach) changes from page to page thus it's not advised to post the local business schema in the header.
You can post a regular schema in headers but avoid Local Business Schema
To do it in kallzu theme, visit your dashboard
Kallzu --> Theme Options --> Site Settings --> Header
Insert your schema in the box and save