L.A.’s unemployment rate dipped to 8 percent last month as the county gained 28,000 jobs, mostly from teachers returning to schools after summer vacation, according to state figures released Friday.

The Employment Development Department reported that the county’s jobless rate fell slightly in September from 8.1 percent over the summer months and was down sharply from 9.7 percent a year ago. The rate is now at its lowest point in more than six years.

But the rate is still above the statewide average of 7.3 percent and well above the national average of 5.9 percent. And in the county’s two largest cities, Los Angeles and Long Beach, the unemployment rate was even higher, at 8.6 percent.

Roughly 24,000 more Los Angeles County residents reported they were working in September, but that was offset by 19,000 more residents looking for work.

September’s employment payrolls grew to just under 4.2 million, regaining all the jobs lost over the summer months.

Almost all the net job gains came from the education sector as a net 25,000 employees – including substitute teachers – returned to school following summer vacation. After adjusting for these seasonal job gains, EDD figures show payroll employment in the county was unchanged from August.

Other industries showing net job gains in September included professional/business services – up 3,800 – and construction – up 1,500. Financial services, leisure/hospitality and entertainment posted slight declines.

Over the past 12 months, county employers added 74,000 jobs to their payrolls, for a growth rate of 1.8 percent. Professional/business services was the biggest gainer, adding 31,000 jobs, followed by health care/social assistance, which added 16,000 jobs.

Hiring in these two sectors has been “red-hot,” according to Brandi Britton, Los Angeles regional director for Robert Half International, a Menlo Park staffing firm.

“Companies that had put software upgrade and other projects on the back burner are bringing those projects forward now and staffing up,” Britton said. “They are showing more optimism about their industry growth and their own growth.”

Even better, she said, some job candidates are now receiving multiple offers and counter-offers, driving up salary levels for the first time in years.

The only weak spot over the past year has been manufacturing, which has shed 16,000 jobs, or 4.4 percent of its employment base.