Hi, Aufilia--
I'd say to go and observe in the kindergarten and first grade if you can. K curriculum is so different from place to place. I think if you're there for an hour or two, you'll be able to decide where you can imagine your child being. Keep your eyes open for outliers and squirmy kids, and see how they are treated in these environments. Watch what academics they're doing and whether anyone is getting differentiated work.
I'd take the ADHD very seriously and start the educational eval process through the school district. ADHD in early grades is very tough-- especially if the child is bored. Kids this age usually don't really have the maturity to "look like they're paying attention" if they're not interested in the work, and with ADHD (depending on type and individual presentation) it may be hard to focus *even if the child is interested in the material*. This may drive everyone, including the child and certainly the teacher and parent, crazy.
ADHD actually makes it more important to place the child in an environment where the academics are at the correct level. If this means subject accelerating a kindergartner into first grade math, I'd probably consider that.
