I'd say the groups are too easy to guess without figuring out (i.e. there's only four names, and four two-letter abbreviations), and the school subjects should be capitalised... try to make some overlapping items later, e.g. you could have had "Carol" as a person so there were five possible Christmas items, or had an abbreviation group with an "X" so the particles/rays weren't so obvious, or put in singers with "Oxide" or "Neutrino" who look like they're in the particle group... otherwise good quiz!

Agree with previous comment. Groups were easy to separate. But I only identified Christmas...
Crossovers/red herrings always add interest and complexity.

this was an easy, not medium. Bit boring I'm afraid, no game play to it. Good variety of subjects though.

Not a single red herring. Groups solves themselves for the most part.

Basic

Too easy-done in 30 secs,no cross-over clues. the only line name I got wrong was because they should be written RE,IT,DT,PE (IMHO.)

Easy to solve the grid without understanding the sets