Students dropouts has become
...dropouts have become/ dropout has become
Even though most students complete schools, it is conspicuous that many pupils quit schooling and indulge in many activities.
... this sentence has a problem with your logic; you say many complete schools and again they quit ... It's better if you re-phrase this line
Firstly, the reasons for school dropouts can be discriminate as: external reasons as well as internal reasons.
..."discriminate" means treating somebody unfairly because of prejudice. So, it is inappropriate to use here.
First, the reasons for school dropout can be categorized as external reasons and internal reasons.