I think am interested in becoming and elementary school teacher.
This is school  for children between the ages of 4–11 and coming between pre-kindergarten and secondary education.
Do you know if it is the same worldwide? 
Yes it is, as at 2001 there there were 92,858 elementary schools (68,173 public, 24,685 private) in the USA
I think elementary school is very important for the child development, do you know what are the most important subjects tough there?
Yes it especially from  from grade one through grade eight.
I wonder what would be the requirements to became and elementary school teacher. Do you have any idea?
The curriculum covers basic arithmetic and sometimes rudimentary algebra in mathematics, english proficiency so a teacher would need to be a certified teacher in these areas
And how can I become a certified teacher?
. It is usually from kindergarten through fifth grade.
Curriculum.
Primary education tends to focus on basic academic learning and socialization skills, introducing children to the broad range of knowledge, skill and behavioral adjustment they need to succeed in life – and, particularly, in secondary school.
In general, a student learns basic arithmetic and sometimes rudimentary algebra in mathematics, English proficiency (such as basic grammar, spelling, and vocabulary), and fundamentals of other subjects. Learning standards are identified for all areas of
Elementary school (United States)
An elementary school is the main point of delivery of primary education in the United States, for children between the ages of 4–11 and coming between pre-kindergarten and secondary education.
In 2001, there were 92,858 elementary schools (68,173 public, 24,685 private) in the United States, a figure which includes all schools that teach students from grade one through grade eight. According to the National Center for Education Statistics, in the fall of 2017 almost 35.6 million students attended public primary schools