SAN DIEGO -- Students, teachers and staff kept away by wildfires will begin returning to class this week.

All public schools, from preschool to college, and most, if not all, private schools shut down in San Diego County last week as the Harris, Witch, Poomacha and Rice fires raged. Monday, 23 of the county's 42 public school districts resume classes, according to the San Diego County Office of Education.

The San Diego County Board of Education gave districts the discretion to open on a district-by-district basis. Those not opening Monday are set to open in the next couple of days.

Some schools needed more cleaning than others because they were close to fire sites while others must be straightened up after being used as evacuation shelters.

School workers will have to "wipe everything down" to make sure campuses are ready for students, said Bob Watkins, president of the San Diego County Board of Education.

Although classroom work will resume, physical education will be limited because of foul air resulting from the smoke, Watkins said.

The wildfires collectively burned nearly 350,000 acres, killed seven people, injured 116, destroyed nearly 1,600 homes, damaged 320 and forced 640,000 residents from their homes. More than 8,000 firefighters battled the blazes at a cost of $31.1 million, Cal Fire officials said.

Public school districts reopening Monday include Alpine, Cajon Valley, Cardiff, Chula Vista, Coronado, Dehesa, Del Mar, Grossmont (except Steele Canyon, which resumes Tuesday), La Mesa-Spring Valley, Lakeside, Lemon Grove, Mountain Empire (except Potrero and Mountain Meadow Continuation, which resumes Nov. 5), National, Poway, Rancho Santa Fe, San Dieguito, San Ysidro, Santee, Solana Beach, South Bay, Sweetwater and Warner.

Public schools reopening Tuesday include those in Carlsbad, Escondido, Oceanside, Ramona, San Diego Unified (except for Palomar Outdoor School, which is closed until further notice), San Marcos, San Pasqual, Vallecitos and Vista.

Public schools resuming Wednesday are Bonsall and Valley Center-Pauma.