Some juveniles who are convicted of burglary in Montgomery County will get a taste of jail--instead of the probation that nearly all first-time offenders now receive--as part of a crackdown on teen-age crime announced yesterday by Montgomery County State's Attorney Andrew L. Sonner.

Young offenders selected by juvenile court judges for "Operation: Last Chance" will report to court officials on eight weekends, beginning with a brief confinement in a jail cell, Sonner said.

The prosecutor said the program will give judges an alternative between detention, which is seldom ordered, and probation, for offenders under 18. Sonner said juveniles committed more than half of the 4,808 burglaries reported in the county last year. Sonner said 95 percent of those who were first offenders were placed on probation.

"What we're saying to the juvenile is that 'We're giving you one last chance before you're sent to jail,' " Sonner said yesterday. "After a youngster has completed the program, he'll sit down and talk with an assistant state's attorney who will tell him, 'We'll be watching you. We have every confidence that you won't do this again. But if you do, watch out.' "

Sonner said the program, which is expected to enroll about 10 juveniles a month between the ages of 15 and 17, will begin with the youngster spending two hours in solitary confinement at the county detention center. "From that experience, we hope the juvenile will get some idea of what being in jail is really like," Sonner said.

After being released from the cell, the offender will discuss the experience with his parents, and an official of the program will outline the rest of the program to the juvenile and his parents. The prosecutor said the educational part of the program will include films, discussions and other exercises designed to make the youthful offenders aware of the horrors of prison life, the difficulties ex-convicts face in society, comparisons between the juvenile and the adult court systems, and the impact of burglary on the life of the victim.

"We're not trying to use the 'Scared Straight' approach where you throw the juveniles in jail and throw bottles at them--anything to convince them that jail is bad," said Charles Day, director of Last Chance. "We want the juveniles to understand the ramification of a conviction for their crime down the road, by sitting in court when someone else is being sentenced for burglary or by sitting in on an interview of a burglary victim."

A similar program, called "Jolt," was begun four years ago in Prince George's County. But Juvenile Court Judge David Ross said yesterday it fizzled last year because the jail became too crowded to accommodate the one-day jail experience and because judges using the program generally felt it was ineffective.

"The Jolt Program turned out not to be a deterent to juvenile crime," Ross said. "We found that most kids bent on crime were going to do it no matter what. We think now that the key to changing a youngster's behavior is encouraging the family to help the child."

Daniel Cassidy, a former Prince George's prosecutor and arch political opponent of Sonner, who will announce today he will seek a fourth four-year term as prosecutor, said the Last Chance program is not tough enough.

"When juveniles get to the place they are breaking into people's homes they've already had their last chance," Cassidy said.

But Juvenile Court Judge Douglas H. Moore Jr., one of the two Montgomery County judges who will carry out the program, said he feels Last Chance has merit.

"It is hard to speculate. We have to give the program a chance," Moore said. "For some juveniles, the arrest and probation alone are enough to deter them from further crime. But others can be sent to a training school and get out and go right back to committing offenses. I think we'll have to wait and see."