I once hired an instructor trained by Halls and he was very good. He was a young Navy guy, a perfect example.
I agree with Matt83, shop around though. I earned my instructor ticket at a similar program back in 77 in San Diego, the NASDS Instructor College. It was very good and very expensive.
Another way to go that can be very good is to work through an in-house IT. Most of the instructors that worked at the store I managed went this route. I trained 11 of them, then they completed their clinic with NASDS or SSI Headquarters staff, much like the IE programs today.
Noticed you are in NH. TDI/SDI is in Topsham ME, you might view the website
International Training :: Home :: :: English.
Chad