転校生 (てんこうせい/tenkousei) Transfer student who is transferring out.
転入生 (てんにゅうせい/tennyusei) Transfer student who is transferring in.
Summer happened and now there’s at least two new kids in every grade, it feels like. It’s cheaper to move in summer. So, it’s not just you. That unfamiliar kid you spotted last month really was new.