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 in August. But it was down sharply from 9.7 percent a year ago and is now at its lowest point in more than six years.

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. Other industries showing net job gains 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 upgrades 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.

The city of Los Angeles saw its unemployment rate fall to 8.6 percent from 9.4 percent in March.

Among large cities in the greater Valley region, Lancaster reported the highest unemployment rate for September at 11.1 percent, down from 12 percent in August. Nearby Palmdale had unemployment of 9.7 percent compared to 10.6 percent in August.

In the east San Fernando Valley, Glendale had 6.7 percent, a decrease from 7.4 percent in August and Burbank had 6.3 percent, a downtick from 6.9 percent in August. Santa Clarita reported 4.7 percent, a drop from 5.2 percent in August.

The Los Angeles area continues to trail the state which posted a 7.3 percent unemployment rate in September, while the nation’s rate was 5.9 percent.