Schools’ efficiency is a matter of question, because, for example, there have been some people who have dropped out of school but have still become successful in life. Therefore, I believe that there are many factors, apart from educational achievements, that can lead to an individual's success.
The first sentence is a bit tricky. It sort of works but it feels wrong. I might go with "the effectiveness of school-based education is debatable, because,.....
"efficiency" just feels wrong