Tell a child to count. He would parrot '1,2,3,4,5....'
India discovered Zero but problem with Indian education today is that children are taught how to count from 1 and not from 0. That is why mathematics is fear-inducing for most children. They have not been familiarized '0' at a young age. The strange looking '0' is introduced only in the higher classes.
The problem is indeed grave, because teaching the concept of zero to a pre-class 1 student is an uphill task. Seems abstract that that age. But nothing could be further from truth.
Before I propose the solution, realize that 1 is easy. It has to do with its grammatical English counterpart 'I' (that is why the symbolism is also so similar!) There are examples of 1 and I everywhere - 1 computer, 1 apple, 1 pencil etc. With one (I) comes the desire of me, mine. It is a very natural and accepted social setting.
You can start making '0' or a 'o' (circle) by starting from a point and ending at the same point so that Zero means 'no entry'. Nothing can enter it.
This is the theory part of zero, like when you add anything from it or subtract anything from it, nothing changes because it is 'no entry'. Let us leave further concepts of 0 to Mathematics teachers of higher classes to explain how multiplication with 0 becomes 0 and division with 0 becomes infinity.
'0' however has to be experienced. You cannot teach a child 0 without him experiential learning. The concept however turns into easily graspable experience - when you bring the child to nature.
How do you show the concept of 'zero' to a pre-school child?
The pre-schools have to bring the child and the mother to a Gaushala to experience zero.
This is how 2 becomes 0. While 'a' calf and 'a' cow' - are individual units - they come together to love and be loved and thus becoming 'one' unit that cannot be entered.
Try coming close to a desi cow when she is in this position with her calf! You will know why 'one' cannot come close by experience.
There are many other examples in nature of how each animal can show '0' behavior and '1' behavior' but the experience of '2' becoming '1' and 'o' is unique to the desi cow.
If you are interested in opening a pre-school for value based experiential learning / homeschooling - you can consult with me - I will be happy to be a part for a small donation to my NGO - Desi Cows For Better India Trust - as my charge for the time.