For ages 6 to 12
Wiz Sudoku for Kids
3 books · 4×4 to full 9×9 · graded by age
A three-book bridge from colour-friendly 4×4s for six-year-olds, through 6×6s, to proper 9×9 grids by age twelve. No time pressure, no scoring, just five grids per page and answers in the back.