You have a point. But the education system is not just the end product. There are many stake holders: students, parents, Singapore, etc. There are processes, infrastructure and people like school leaders, teachers, MOE staff.
Result is only one part of an education system. Values, integrity, empathy, compassion, teamwork, fortitude, character, care for others, teamwork, excellence, etc are outcomes of an education system.
Looking at our school today, do students enjoy their education? are teachers empowered to teach and do they enjoy teaching? are the learning processes in our education system enriching? do principals identify themselves to mould the next generation or are they in for career and their own glory? is the product of our education system well rounded adults or are they self seeking? look at how the average Singaporean behave!
All these give you a good idea how our education system fare