For about 10 months beginning each September, Tom Wines trains Prince George's County high school students in employment skills. Then, about the time his seniors are adjusting their mortarboards, Wines starts concentrating on his summer charges--golden retriever puppies.

"There's no backtalk, for one thing," says the 31-year-old Wines of the puppies he raises to sell. "They're real cute all the time. The worst thing they do is bite your pants leg."

Wines is not in this business for pleasure alone, however. Like many other school teachers, he works to supplement his teaching salary during the summer months.

In search of summer employment, teachers in this area have traded their white collars for a variety of uniforms, with a good number opting for jobs at swimming pools. One Prince George's teacher dons a parachute on weekends to teach people how to jump from planes, while others sell everything from athletic supplies to bee pollen.

Teachers union leaders here estimate that about half the area's secondary school teachers are working this summer, while a poll taken nationally in 1974 indicated that about 42 percent worked during the vacation break.

In Prince George's, teachers earn a median salary of about $26,000 a year after 14 years of service; pay scales in other local school systems are slightly higher. Most jurisdictions allow teachers to stretch their salaries for the nine-month school year over 12 months, but teachers often elect to be paid from September through June only.

"I can budget myself, so why should Arlington County have my money for the summer?" said Sarah Sullivan, a summer real estate agent.

Nationally, 70 percent of secondary school teachers are women; nearly all the female teachers interviewed here were their own sole support.

"We still have a number of people who are single parents," said Prince George's teachers union president Paul Pinsky. "You have to bring in the money to feed the children."

"Teachers do have to supplement their incomes by any means necessary," said Luther Shelton, a District teacher for 19 years.

"I have held some tough kinds of jobs: dishwashing, construction work, you name it," Shelton said. This summer he is teaching in a special summer school enrichment program in Southeast Washington. Shelton, who is active in the Washington Teachers Union, said that younger teachers are the ones who need the work most in the summer.

"It's the younger people at the low to mid-range of the salary scale--it's almost a necessity for them to work," he said.

"I've heard more and more people say it's a terrible way to live because they can't handle their paycheck in a way to save enough to live for the summer."

Shelton could have been talking about special education teacher Kathy Larner. A divorced mother of two with only four years of service (compared with the median of about 14 years for teachers in Prince George's), Larner said she has tried to get by for the summer by saving $100 a month from her paycheck, but it hasn't worked.

"I always try saving, but something always comes up," said Larner, who is working 20 hours a week this summer finding jobs for disadvantaged and handicapped teen-agers as part of a county summer jobs program.

Last year her savings were drained because she attended a teachers' convention in California. This year it was legal fees connected with a child-custody fight. Her summer job, which takes her from fast-food restaurants to shopping malls to supermarkets in an unair-conditioned car all day, brings in only a third of what she makes in the winter.

"I cut corners," Larner said. "We get away with cold food and tacos in the summer and go to $2 movies," she said.

Larner said that summer jobs are also hard to come by for teachers, especially during the current bout of high unemployment. For that reason, when they can find them, teachers tend to return to good jobs.

For example, Gary King, who teaches deaf children at Eleanor Roosevelt High in Prince George's during the school year, manages a private pool in Rockville six days a week during the summer. King, 32, has worked at pools for 14 of the 15 years since he graduated from high school in 1968.

"It's like entertainment," says King. "Any time you're involved in entertainment and keeping people pleased, you have to be charming and you have to work weekends."

King, who gives private swimming lessons in addition to supervising six lifeguards, also enjoys dressing down for work. At about $6 an hour, though, the pay is lower than his teaching salary, he said.

Arlington math teacher Sullivan values her real estate work as a way to get ahead in this world, on her own terms.

"I want to go to Europe and any number of places," she said, but she works to have "a security net under me so I don't have to be dependent on anyone."

For those who do not have to work, however, travel remains one of the primary interests of teachers in summer.

Pam Gardiner, who teaches at Concord Elementary, will be striking out for Oregon this summer with another county teacher. Gardiner, 42, who has taught school for 18 years, said she would be working during the summer like other teachers if she didn't live with her parents.

"In my youth of teaching I taught a lot of summer school," said Gardiner, as she packed her car for the trip. "I did eight summers at the beach as a cocktail waitress." She said she has acquired wisdom enough to know that even a teacher has only so many summers in the sun.

"It's age, learning to economize, and a different life style," she observed. "Summer is the time to rejuvenate myself, to learn and explore."