Oh my I remember fighting about that (the Fremch version but same problem) with a teacher in middle school. We were taught to change verb each time and I hated the results, and being the annoying kid I was, I brought random classics to prove my point
Retrospectively I realize I was stupid, because the main point of the teacher was to expand our vocabulary, not making the kids good authors. I've never been a fan of dumbing down or not telling kids WHY they learn things, though.
As @elyss said, in my opinion it should be kept for specific moments. For eg. If there is a brutal change of reaction of an interlocutor on a dialogue (eg. Goes from calm to alarmed), then yes, that's the time to put a more precise, stronger word than said.