Bookmarking. Mine are starting kindergarten this fall and I have to make the same decision. They were together this year in PreK and were happy. One wants to stay together, the other is fine either way. I am on the fence. They are identical twins which I know will make it harder for teachers and other students.
My identical triplets girls stayed together through 2nd grade then split after that. Then we homeschooled beginning in 8th grade. They are now sophomores in college. I will say the only frustrating part was in combined classes like music, PE, etc., some of the teachers did not get to know them. The PE teacher for instance just called them all by their last name because he never wanted to learn their differences even though he saw them at different hours during the school day. To this day, they still remember that he called them "Cross" and never by their first names. They hated that.
I will say that it's very difficult to get to really know kids in 50 minutes once a week, and exceptionally difficult to learn to tell identicals apart when you never see them together and/or see them infrequently.
I try really hard with our identical twins but I have 850 names to remember, and it's hard enough with the ones who don't look exactly alike. I have a set of fifth grade girls that I am finally able to tell apart this year after five years of having them in class, only because one has put on a little weight. With the identicals in 4th and 3rd I have no idea which one I'm addressing unless I look at the seating chart. I assure you it's not for lack of interest in them as individuals.
Ours were in the same class in preschool then in K we had them in classes where the teachers were in adjoining rooms. That meant that they did all out of class activities together - Recess, PE, field trips. Worked great!
I think I will check with the school to see how the kindergarten classes/teachers interact. If they work as a team or pairs or adjoining classrooms (as mentioned above), I'd be more comfortable about having them in different classes. They'd still have time apart but also time together during the day. It would also help on the convenience side of things for me, if they tend to stick to the same homework schedule, etc.
Their pre-k teacher got back to me and said she thinks they'd be fine either way. She said: They don't really interact much at school; they each have their own friends and have a pretty strong autonomy in the classroom.
Not a twin mom, but did volunteer in kindergarten where there was a set of twins. They were boys, immature and fed off each other. If one was upset, the other got upset seeing the sibling upset and more than once chaos ensued with them upsetting others in the class. It was an interesting dynamic for sure.
One of my kids was best friends with a set of twins. Sometimes they were in the same class, sometimes not. Didn't seem to matter to them, they were good either way. They did hang out with the same kids for the most part though.