There is a rule about gifting teachers that gets ignored constantly: the gift should be small enough that it does not look like an attempt to buy influence. Many Indian schools have written policies about this, and even where none exists, a teacher who receives something expensive from one student's family has a problem, not a present. Under ₹1,000 sidesteps all of it.
A pen is the traditional answer for a reason. The Parker Jotter at ₹272 is the cheapest item on this page and still the one most likely to sit on a desk for a decade, because it is refillable with standard Parker refills rather than disposable. It is also the gift least likely to be misread — nobody has ever been made uncomfortable by receiving a pen.
Journals are the other obvious category, but note what separates the four here. The Cavalo and the Alokik are plain notebooks — magnetic flap and strap closures respectively — and read as work tools. The Wemate and Xiyunte both come with a three-digit combination lock, which turns them into personal diaries rather than desk notebooks. For a teacher you know only professionally, the lock is the wrong register; a locked secret diary implies a kind of intimacy that a student or parent should not be signalling.
The Oh Cha tea box at ₹580 is the pick if you want something that gets consumed and leaves nothing behind. Six blends in small glass jars, which she can keep in a staffroom drawer. Worth noting that the listing itself is inconsistent — one bullet says five blends, another says six and lists them, and the two lists do not fully agree on the names. The title says six flavours, so that is what to expect.