THE ancient Greeks, in their wisdom, believed that only at evening could you recognize how wonderful the entire day had truly been.

In that same vein, now that Schools Chancellor Joel Klein’s historic eight-plus years at the head of our public school system are drawing to a close, it’s possible to appreciate the dramatic and fundamental transformation of our schools that he has helped bring about.

Think back for a minute to the old status quo that we confronted in 2002.

It was a system top-heavy with bureaucracy and shot through with patronage, where authority was diffused and confused and where, ultimately, no one was held accountable for making sure children learned.

Just as there are today, there were a lot of outstanding principals and teachers in the schools then — but all too often, their excellent efforts went unrewarded, just as the half-hearted work of others too often went unaltered.

And the result was a school system that failed far too many of our kids.

Seizing the opportunity that came when state leaders finally gave New York City control of our own schools, our administration, led by Deputy Mayor Dennis Walcott, Chancellor Klein, and their teams, changed all that.

We reduced the system’s bureaucracy and plowed the money that was saved back into the classrooms.

We made sure that for the first time ever, every school in the city got a fair budget deal from City Hall.

We sharply reduced crime in the schools.

We oversaw the largest effort in the city’s history to construct new schools and modernize existing ones.

We created new, academically challenging schools, including charter schools, that give students a broader range of educational choices.

We established standards-based arts education for students at all grade levels.

We opened up new channels of communication between schools and parents.

And we ended the long-discredited practice of social promotion that had set up generations of students for disappointment and failure.

The result: Even though we still have a lot of work ahead of us, any way you measure it, our schools today are far better than they were eight years ago.

Graduation rates that were once stagnant have gone up every year; they’re 27 percent higher than they were four years ago, compared to a just 3 percent rise in the rest of the state.

Our students have shown significant improvement on the National Assessment of Education Progress tests.

Black and Hispanic students have shrunk the achievement gap separating them from their white and Asian classmates.

And a school system that was once the poster child of dysfunction is now hailed by the Obama Administration as a model for other big cities to follow.

A lot of our school reforms were initially controversial.

Today, they’re widely accepted.

That shows how far we’ve helped move the debate about improving our schools, here and across the nation.

Joel’s leadership has been a huge part of that.

Now our new schools chancellor is Cathie Black — a dynamic manager with outstanding achievements in business and a deep understanding of the skills our students need for success in college or careers.

I’m confident that she’s going to keep moving our schools forward.

And that’s why last week I was delighted to welcome her on board, along with two other new city commissioners: Edna Wells Handy, Commissioner of the Department of Citywide Administrative Services; and Terrance Holliday, Commissioner of the Mayor’s Office of Veterans’ Affairs.