Yonathan, your grammar mistakes are mostly about singular and plural. Please be more aware about that, since grammar also the consideration from the examiner to reach a high band score. I think the flow of ideas is well-done. My suggestion is that you need to consider in your conclusion that you should mention your clear stance about the issue not just mentioning 'believe that', because a band 6 score of above in writing band descriptors mention about 'a clear position towards the issue'. For a breakdown of your grammatical problems, and corrections applied.
Formal education become
formal education becomes
at four age
at the age of four
children can get more than a thousand information during the age of three to five.
children can get thousands of information during the age of three to five
many memorable moment
many memorable moments
Gajah Mada University researchers says
Gajah Mada University researchers say
many problem
problems