Philadelphia schools chief Arlene Ackerman gave herself a couple of A's and a B for her first year on the job. A more accurate grade is an Incomplete.

Ackerman seems well-intended and has said many good things about fixing the failing school system. From Day One, she has taken a tough stance on key issues.

While voicing a sense of urgency, however, Ackerman has been slow to set in motion the sweeping changes needed to boost overall student achievement.

With a 50 percent dropout rate - among the highest in the country - and 85 failing schools, there is no time to waste. Too many students are being left behind while administrators work on the latest plan to fix a broken system.

It took nine months for Ackerman to announce her first major policy push - "Imagine 2014." In the life of a child, that's one school year.

The ambitious five-year strategic plan calls for closing poorly performing schools, reducing class sizes, and overhauling teacher hiring. It also proposes a weighted student-funding formula that would give more money to the schools that educate the city's neediest students.

The plan has merit and would drastically change how the district operates and its culture. But the proof rests in the implementation, which hasn't begun.

This week, Ackerman boldly vowed to crack down on teachers, principals, and central staff who are not up to snuff. They will either be fired or disciplined.

Ackerman has the right idea in holding accountable those responsible for educating the city's 167,000 public school students.

Last year, "unsatisfactory" ratings were given to only 13 teachers among a teaching force of 10,700. Five were removed from their jobs, while none of the nearly 300 principals was removed for not meeting academic standards.

Ackerman knows that tighter discipline will ruffle some union feathers, but she doesn't seem afraid to take on the establishment. She also deserves credit for cracking down on violent students and ordering expulsions for the first time in three years. But more must be done - and faster - to make schools safer.

Ackerman still has an extensive to-do list with no time to waste. Once she gets results, then she will have made the grade.