"Since the very first lesson she has established herself as a very active student with bright ideas and non-standard thinking and continued likewise throughout this whole academic year."
What I want to say here is that the act of establishing herself took place only on the first lesson, but I am afraid that the way I've phrased it it may sound as if she kept repeating this act every lesson.
Are my fears justified?
If yes, what's the most natural way in English for expressing my thought here?
You're right, "since the very first lesson" would mean "all the time from the first lesson until now". It's not the same as "in the very first lesson".
What you need for the meaning I think you're looking for is:
"In the very first lesson she established herself as a very active student with bright ideas and non-standard thinking, and she has continued likewise throughout this whole academic year."
("She established", but "she has continued". I can't exactly explain why; if anyone else can, feel free to edit or post a new answer.)
