how will the secondary students affect my childrens that are in kindergarden

Thank you for writing this article! I was in the first group of parents you talked about. I was also naive when I sent my first son off to kindergarten.
In my local school district the parents have the "choice" to send their child half day or for full day kindergarten. My husband and chose the half day for our son as we thought that was what was in the best interest of our son. From the moment I met my son's teacher the half day option was a bone of contention with her. She and the school secretary hounded me just about every on when I was going to change my mind and send my son to the full day of kindergarten. A couple months into the school year my husband and I were called into Child Study Team meetings to discuss our son's behavior in school versus at home. The teacher and the school psychologist came up with two diagnoses/labels for our child without even testing him (NVLD and visual perception issues).
In one of the meetings the school principal came out and said that our son needed to go the full day of school because kindergarten is the new first grade and certain things are expected of children, so our son would be retained if he did not go for the full day!!
My husband and I ended up making our son attend the full day. The school claimed that all of our child's issues disappeared within a few weeks of a full day of kindergarten! Weird.....
I do admit that my son did cry a lot (for good reasons though). I was told he didn't follow the teacher's 3 to 5 step oral directions. He did have trouble cutting, writing, erasing correctly, doing his worksheets independently, coloring with the "right" colors, drawing non stick people (not allowed to draw stick people) and houses. He also had trouble dealing with the bullying. They put him in social skills class with the bullies 30 minutes once a week. I worked on his fine motor skills at home.
That year my son taught himself how to tell time on an analog clock (not taught at school that year). He also learned to read, but he was on his way even before he entered kindergarten.
My son is no longer in that particular school for many reasons.
Also, the students at that school had 20 minutes allotted for lunch. By the time the kids sat down they really only had 15 minutes to eat. There was also a "mandatory no talking time" the last 10 minutes of lunch, so the kids could finish up. If the kids talked during this time stickers were taken away from their grade level chart and half of the lights were shut off. Many of the little kindergartners were very frightened of lunch. My son included. He scarfed down his food extremely fast and never talked at all. He was too afraid to talk even when my husband and I came to volunteer.
oh ya...the very first week of school the school sent home a kindergarten memo stating "be assured your child will NOT be playing all day". I was sad to hear that.