With my oldest, I didn't closely monitor pre-school and kindergarten. They taught her how to read using sight words. I had my worries, but I didn't launch a full intervention until first grade.
They taught her guessing as a way of life, and my last 7 years has been a war against guessing: guessing in reading, guessing in math, guessing in music, and guessing in sports. I've done rather well in the battle, but it's been a battle. Honestly, if I had to do it again, I may start with teaching Attic Greek at 3 or 4 because since it's all foreign, there is no illusion of effective guessing or using context clues.
I got to my younger two before they got infected in kindergarten, but MAN, this long war against guessing has been one extraneous struggle in my life.