Andre, I will try to focus on grammar and semantic aspects and remain as faithful to the original piece as possible:
A very well-known catchphrase states that “knowledge doesn’t occupy space”. In this sense, I would say that there will always be a need / demand for new schools. I, thus, support (or "For that reason I support...") the building / construction of a new high school. There are a lot of positive things that are a new high school can offer and only a few problems.
Nowadays, there are several different approaches to education. A new high school can, much more than an older school, bring to life (or bring alive) new ideas and approaches. Older schools are generally stuck in traditional methods and, if the system is working properly ("working out" has a different meaning), there is no problem with it. However, any new high school offers a big opportunity to start things in different ways and, in this sense, is much more free to experiment with new ideas. For example, I am a student at [name] University, a brand new university (it has only about 5 years of existence). People who have thought about how [name] University would work have had the opportunity to introduce things that don't exist in any other Brazilian university, like interdisciplinary courses / programs, new subjects and so son. On the other hand, the older universities, despite having an impressive reputation, struggle to introduce these differents views.
In addition to the possibility of different approaches, I believe that the building / construction of a new high school is positive because it can employ more people and meet / satisfy the demand for education that exists in the community. In fact, where I live, there are a lot of teachers searching for jobs due to the lack of schools. Even those who aren’t directly linked with education are sometimes employed in distant areas because there are not enough job offers in my neighborhood. Therefore, the creation of a new school can employ not only teachers, but also many other professionals.
Some people say that we need to stop building new schools and focus on the quality of the schools that already exist. It seems to me, however, that this is a misconception. A new school can create more competition and therefore improve the education system.
So, all things considered, I think that the building of a new high school is /represents an important event in the community and should be supported by people who live in the neighborhood.
Andre, your English is surprisingly good and your writing is very cohesive. Two things I'd like to observe:
1) I noticed you have a tendency to pluralize certain adjectives (olders schools, differents approaches etc.). In English, adjectives must maintain their singular form, regardless of whether or not the following noun is a plural. If these were typos, you can disregard this comment.
2) While I wouldn't consider the use of "so" in an essay to be wrong or necessarily inappropriate, you may want to consider using alternate connectors for a bit of a change. These could include "therefore", "hence", "consequently", "as a result", "thus" (as I see you have), among others. The use of such substitutes helps enrich your writing and should make for a better reading experience overall.
Great job nevertheless. Keep it up!