Are you talking about the kind of Kindergarten that starts at the age of 3?
(In Germany it would probably not be a good idea to teach your kids how to read before they go to enter school (at age 6 or 7). Schooling is mandatory in Germany, and elementary school is boring enough if you don't already know the stuff they are trying to teach you. If you have more choice for your kids, then reading earlier may or may not be a good idea.)
I don't see why it would be a bad idea, many kids seem to fail to learn to read well if the task of teaching it is left to the school.
FWIW, I could read when I started school (at 6, in Austria [1]), as well as do simple maths; I was bored pretty much throughout my education, but at least I did well. Bored & lagging behind surely must be worse.
[1] homeschooling is permitted here but it's extremely rare as far as I know.
(In Germany it would probably not be a good idea to teach your kids how to read before they go to enter school (at age 6 or 7). Schooling is mandatory in Germany, and elementary school is boring enough if you don't already know the stuff they are trying to teach you. If you have more choice for your kids, then reading earlier may or may not be a good idea.)