How do you balance worksheet difficulty for grades 1–8? Looking for teacher insight.

I'm working on a small tool called SheetMate that generates printable worksheets instantly (math, reading, spelling, etc.).

It started as something for my stepson, but now I'm expanding it — and the hardest part so far has been dialing the right difficulty level for each grade.

Teachers / educators:

• How do you decide whether a worksheet is too easy or too hard?

• Are there any red flags that instantly tell you the level is wrong?

• Do you prefer shorter worksheets with fewer questions or longer sets?

Any insight would help a lot — I'm trying to make this genuinely useful for real classrooms and parents.

Thank you!