What is meant by: "He felt something much more keenly"?
Solution 1:
I haven't read the whole piece, but from what little I read, I assume Anne to be a teacher, who, just prior to this quote, witnessed the "trained crickets" belonging to Morley, whom I assume to be a pupil.
I interpret it to mean she "stood him on the platform" as a form of punishment and took his crickets, a punishment that hurt him more than the platform. That is, he wasn't much bothered by the first punishment, but the second was more intensely punishing.
As Merriam-Webster defines keenly,
2b of emotion or feeling: INTENSE