Re: Academic difficulty in college
I'm another one of those "easy A" high school students who struggled more in college. My first semester my grades dropped one full point from my high school average - and that doesn't include the course I took an incomplete in. They improved for the next couple of semesters, then I went through a period of severe "academic indigestion" (love-life problems, didn't care for the courses, etc.) My last two years I finally got my head on straight (plus had the interesting senior-level courses) and carried a high-B/low-A average. All of this was in a competitive engineering school.
There is an interesting side-light to your question that occurs in engineering curricula. All accredited engineering programs require some sort of 'capstone' design experience in the senior year. This means they are presented with an "open-ended" problem to solve that may or may not be completely defined. Furthermore, this project should require the students to draw on material from throughout their studies, rather than just material from a specific course.
What often happens in this course is that the 'better' students have a harder time with the project than the 'run-of-the-mill' students. Good students are used to being given a well-defined problem, determining the appropriate equation to apply, and generating a solution. They are not used to dealing with ambiquity. The weaker students have generally been "in a fog" throughout their studies, not quite sure what's going on. This project is therefore SOP for them. They've learned to muddle through and somehow get to an answer.
This doesn't mean that the weaker students produced better results than their 'brighter' colleagues, just that they were able to function better in these projects.
Second side note: A quote I once heard - "Be kind to your 'A' students, for they will someday be your colleagues. Be kinder to your 'C' students, for they will some day create their own businesses and fund your new buildings."