By following any of the four schools, we can achieve enlightenment by following the correct path, but that depends on finding a fully qualified teacher who teaches a correct, complete path.
It also depends on past karma, so depending on that, many will follow in that way. It’s directly dependent on past karma which one we follow and learn from. If we live in a village or area where they follow mainly one school, then we follow that which is mainly followed by the people of that place. Basically, it’s dependent on past karma.
We should study one school well and then we can receive teachings that we find beneficial from the other school’s lamas. In this way, our mind and our practice won’t get confused.
We can study the four schools and then check our feeling, where it is stronger or which one we feel closer to. This could take time. We can study just roughly, then we can check.
After so many years of following different lamas and teachings and schools, even for thirty or more years, there are some who still don’t know how to follow the path to enlightenment. It’s important not to become like that!