Single-digit sums to start, and the generator below scales to any width the class needs. Every sheet downloads with its own answer key.
These are ordinary addition sheets, generated rather than photocopied: pick how many problems, how many digits, and how many addends, and download a fresh PDF every time. The answer key prints as a separate page, so the student copy and the marking copy always match.
Because the sheets come from a seed rather than a fixed bank, a retest never repeats the exact problems at the same difficulty — useful when memorized answers would flatter the result.