I work in the schools and see this all the time. I don't know the whole story but I am already questioning your son's school. Kids in kindergarten are just getting used to the whole school routine. I work with a lot of kids who have attention problems but not necessarily because they have diagnosable ADHD. I would ask what interventions the teacher does for him. Using a ruler to get his attention isn't the most creative way. It sounds extremely old school. Perhaps he is bored? Are you able to observe the classroom? I would be extremely cautious about meds at this point. Most children who have symptoms indicative of ADHD, demonstrate those symptoms across all settings not just the school setting. Even if you were to go to a doctor, a doctor would ask you what symptoms you see at home. If you don't even have many concerns the doctor would certainly question it as well. My biggest concern is for your child in this classroom. Perhaps it's not the best placement for him. Definitely observe him. If the teacher doesn't let you, take it up to the principal or priest (that's who you would go to, right?).
As for the other child...good grief. Perhaps it is a legit case but how was the diagnosis made. I question any diagnosis that come from a regular family doctor. Good doctors will always refer out. There are many possible causes for adhd symptomolgy that need to be ruled out such as an undx sleep disorder (not just insomnia), diet, specific medical conditions, anxiety, etc... In an ideal world, a doctor would order blood work and go over the physical. The child would eat healthy, go to a sleep doctor to rule that out, and also go to a psychiatrist to do a full comprehensive evaluation. Oh, I would also want to rule out learning disabilities and speech/language disorders as well. Lay people like to jump to the easiest conclusion, which is currently ADHD due to lack of knowledge. The teacher's input is important but her advice regarding meds should be taken with a grain of salt at this point because it is not her area of specialty. Please seek out specialists, not just regular family physicians.
If you don't get anywhere with the school, I would consider a different placement. I am not a big fan of moving kids in the middle of the school year but certain unique cases warrant it. I have seen kids with high needs be very successful with certain teachers in the regular education classroom. I have also seen kids who have never had problems just fall apart in other teachers classrooms because of specific factors regarding teaching style, etc....
There are a few kindergarten teachers who frequent this forum. Perhaps they could respond.