It's possible that:
* GTT is a specific program at a particular school or small group of schools: Many schools create their own internal programs or naming conventions. If you encountered "GTT" in a specific context (a school's website, brochure, etc.), providing that context would help determine which school(s) use it.
* GTT is an abbreviation for something else: The acronym might represent a different program or initiative entirely. Clarifying what GTT stands for would be crucial.
* It's a typo or misspelling: There's a chance the correct name is similar but slightly different.
To find out which schools use a program called GTT, you'll need to provide more information about where you encountered this term.