I don't want to get into a discussion better suited for the enthusiatic flightinfo.com pilot boards, but I believe the school "affiliated with Delta" you're alluding to is the Delta Connection Academy. Actually, the only affiliation with Delta is that the airline allows the school to use its name and logo. The pilots at flightinfo.com will give a venomous view of the professional airline's view of DCC....let's just say it's not that favorable. You may also find some discussion about the school at airliners.net.

With the current pilot shortage looming, there's no need to go to a high-priced specialty school that promises an interview with a regional if they successfully complete the program. All that the airlines want to see is a bachelor's degree, the requisite licenses (which are the same whether they come from an instructor at the local municipal airport or a big flight school), and a certain quantity of flight experience. The cheapest way for your son to get his licenses would be from an instructor at your local municipal or county airport. The fastest way is from one of the flight training academies. Of all of those, FlightSafety probably has the best reputation.