They actually learned to write in cursive, as in joining the letters together, in the pre-school/kindergarten lessons. I asked and the reason I was given to learn to write that way and not in blocks was because children naturally make swirls when they draw.
I myself made this transition, from Montessori to a more traditional public school, at about age 11. I was, frankly, glad to have done this, as I was wanting the greater sense of routine and structure. The loosey-goosiness of the Montessori school was not helping me to focus, but the new school environment did.