If you wanted to write an essay on education being the best legacy, you would want to start out by defining your terms. What is a legacy? Your definition might be that it is a gift from the past. And what is education? Your definition might include the idea that it is the imparting of knowledge, skills, and judgment needed to live a productive, mature life.
All information travels from the past to the future -- no information can travel from the future to the past (as far as we know.) As far as we know, all that travels from the past to the future IS information. Shaping the information that is sent to the future might be another way of defining education. The care we take in shaping that information, the wisdom that we are able to send through time, is all we can send that is able to change through time to meet new challenges.
For example, eventually any money we send ahead in time through our wills will run out. But wisdom to use money can last as long as people keep sending the information through time.
We cannot send food very far through time, but we can send the information to grow it and harvest it.
We cannot send morality itself through time, but we can send the reasons for morality and our thinking on morality ahead to future generations. They will certainly change the information to suit their own time and situations, but our wisdom will have survived. Education is our way of hanging on to the accumulated wisdom and knowledge of all the generations of humans who have ever lived. Animals can't do that -- they all have to start over with every generation. We alone can point at our civilizations and see the accumulated intelligence, skills, knowledge of generations before us.
So while we may dislike the process of getting an education (or parts of it at least), it is the best gift, in fact perhaps the only gift, that can travel through time, that must travel through time, that does travel through time.