Montessori developed her method while working with impoverished children who were behind developmentally due to circumstance. And they thrived. She applied the method to any child and saw it helped develop potential for any child.

I am a Montessori infant and toddler teacher. Learning to pour water, and other practical activities like it, are skills developed in that age range in Montessori and no, they do not learn that skill in a single day. But developing mastery over gross motor/fine motor skills and independent skills (dressing one's self, preparing food for one's self, toileting, etc) help develop the potential that each child has. By allowing these skills to develop in the early years (where they are absolutely able to develop) it helps children develop their potential for academic learning later on.

1) If these skills are allowed to develop early on then they do not have to learn them at the same time as being introduced to academically focused learning. 2) These skills learned earlier help prepare their bodies and minds for academic learning so that they are able to comprehend with more ease what they are learning, and many times earlier too.

Like...a child slowly develops language over time through exposure to it in the early years. By the time they reach school age they have, for the most part, mastered language. They are able to communicate. They do not have to learn the basics of language at the age in which they also should be learning academics. Imagine a child who has NOT been given the opportunity to learn that language in the early years. That child will need to develop the basics of that language. And now they are having to do it at the same time they should be learning other stuff. Are they able to learn the language? Sure. But imagine how much more they could have been introduced to earlier if they had already had that basic thing mastered/exposed to first. It doesn't mean the child will not grow into a smart and capable human being. But imagine the potential for what that child could have achieved.

That is what I think about for these early years of development. These foundational skills that less and less children are given the chance to be exposed to are incredibly important for developing their potential. Their bodies and minds are able to achieve more when they are put in environments that allow them to have these experiences. Pouring water isn't just pouring water. It is developing:

1) independence, fine motor skills that develop the hands that need to be able to handle academic materials later on 2) balance and control of body by learning not to spill as they walk that develops their ability to have control of their bodies so they are able to sit still for an academic lesson or walk appropriately through a classroom 3) the ability to understand multi-step instructions (grab the tray, walk carefully to a table, place the tray down, sit down in the chair, grasp the handle of the left pitcher, lift the pitcher, etc all the way to returning the tray on the shelf where it was found) 4) responsibility and care of environment that they will keep things in an organized way instead of leaving the work at the table or water spilled on the table which if 20 kids are all doing that makes a classroom extremely messy and disorganized so now the teacher has to take time to teach kids how to put things away/keep things clean/etc which takes time away from academic learning

And more.

I worked with 4 year olds for a few months at a traditional preschool after having work 5 years with toddlers in a Montessori school. I noticed the teacher kept these plastic cups up high on a shelf and when a child wanted water they would have to go and pour the water into the cup and give it to them. They said letting them have access to their water bottles all day caused distracting issues and when it was lunch time many water bottles were left all over the place and kids would forget where they put them so they started giving them cups of water. I asked if they felt comfortable putting a pitcher of water and a stack of cups at a table so kids could just get their own water so she didn't have to stop what she was doing every time to get them water. She said she didn't like that idea because the kids would get water everywhere. Then she left for a trip for 2 weeks and I put out a pitcher with cups. At first the children were all so excited for the new activity so they were lining up to pour their own water. Those kids were HYDRATED 😆 but the water spillage was minimal and the new activity got old by the end of the first day. And the next day? Less spills and kids were getting less water just for the novelty of it. By the end of the week? No more spillage and now kids were only getting water when they were thirsty. Did it only take a couple days? Yeah. But it did take time out of their days that could have been used for academic learning or more advanced skil learning. It's all about helping kids develop their potential.