Typical of Montessori pre-school education, the children do not bring back as many worksheets/written materials as those in other schools. It doesn't mean that they aren't learning, but just that (1) a lot of Montessori classroom learning is done with the special Montessori materials and may not be easily translated onto paper; and (2) their learning is not restricted to just paperwork and kids are learning through creative ways instead of just completing worksheets.
According to the Montessori's curriculum, a typical child may only begin to learn to write at 4 as their motor skills as well as language and cognitive development may not be ready before that. Hence they don't get any worksheets till then. However, there are children on accelerated programme if the teachers deem them to be more advanced. This means their learning path is personalised and more advanced children will be exposed to materials/content that is planned for older kids. The pros of that are (1) they don't waste time waiting for others to catch up; (2) their interest is always piqued as they are constantly exposed to new materials/content; (3) they learn more in the same time. In a non-Montessori classroom, this simply isn't likely.
Many 4y.o. kids in his school still aren't bringing home any worksheets whereas M started writing in school when he was barely past 3. So every week we get a thin pile in his Friday folder. Of course this helps to assure us of his progress and gives us a glimpse of what he has learnt in school. And it is also at times when he surprises me by repeating what he has learnt in school in the comfort of home, that I get a positive assurance of our choice of his pre-school education. Especially now that I am selecting one for Chipsy.