|There appears to be several definitions for Y-TAC.
Yokohama - Teen Activities Center
Yokosuka - Teen Activities Center
Yokosuka - Teen Age Club
Perhaps over the years it had all those names, but very little is know about Y-TAC.
What we know is that it is known to have existed in Yokosuka as early as 1952, when Dick Cook (Class 52) was it's President. It was called the Y-TAC for Yokosuka Teen Age Club -- also referred to by the Navy as Fleet Activities-Teen Age Club, but it was always referred to as Y-TAC. At that time  it was located on the first floor of a two story barracks type building, in a location called " J " area.
The below map -- from 1961, and indicates the location of the present school buildings -- does show a "J" area in the top portion of the base. Perhaps in the beginning Y-TAC was located there. Hopefully over time an alumni who has all this information will be able to assist us.