<<< My guess/speculation is that very very few students turn down an ED offer, even when the FA comes in low>>>
I wonder what the yield is for ED students who APPLY for aid. I have no idea. I think ED is still the popular route for the full-pays, but certainly those with need are applying as well because we’ve seen disappointed posts. I think you’re right that some are excited by the acceptance and will sign their lives away with Plus Loans and private loans to make it all work out. But, there are a number of people who just can’t do that…poor credit, lower income, whatever.
Overall ED yields are very high, e.g. 97% at Rice. Even if just 10-20% of the ED admits applied for FA, and all the ED declines came from this group, that’s still a 70-85% yield for FA applicants. https://futureowls.rice.edu/futureowls/Freshman_Profile.asp
Even in the days when people perceived ED contracts couldn’t be broken, there were still students who backed out of due to various reasons. I am not aware of any adcom going after any student to make him/her attend the school (law suit). What ED is today is not so different than what it was before. Contrary to popular believe, ED must have some teeth and it must work for a lot of schools/students or the yield wouldn’t be so high. I don’t think it will go away any time soon. My guess is high school GCs that do not understand or adhere to the agreement will continue to tell their students, “I do not understand why our school has not been successful in getting students admitted to College X.”
Both high schools my kid attended put a similar process in place by not sending out any transcript and LORs until after ED decisions were in, except for EA and rolling admission schools. Both schools also used Naviance to track all applications and results. Any school that’s serious about college application will want to make their database as accurate as possible.