Go to a movie theater playing an R-rated movie and you may see unaccompanied youngsters buying tickets with no questions asked. But take your child to a PG-rated movie and you may be surprised with gruesome special effects, excessive violence, or profanity.
It's little wonder some parents feel frustrated about controlling what their children see on the silver screen.
Recent releases such as ''Indiana Jones and the Temple of Doom'' and ''Gremlins'' have spurred controversy about their PG ratings. Many parents felt the violent content and some of the special effects warranted a stiffer rating. A significant number of directors, producers, and theater owners agreed and pushed for a change.
In response, the Motion Picture Association of America set up a new PG-13 rating, which became effective July 1. PG-13 restricts viewers ages 12 or under just as an R rating restricts those under 17.
Jack Valenti, the association president, says the new rating is for the ''increasing numbers of movies that are leaping beyond the bounds of PG but are not quite R.''
The PG-13 rating may help dispel past parental discontent with the rating system.
''I've been disillusioned with the rating system,'' says Susan Jakub, who has four children ranging in age from 6 to 18. ''I've been to PG movies and have seen some obnoxious things. Other parents say the same thing. You really can't rely on the (rating system) and you get fed up with it.''
She also questions the discretion of movie theater managers. ''My 12-year-old walked into an R-rated movie this week,'' Mrs. Jakub says. ''Theaters are supposed to enforce the ratings but they don't.''
Jim Huston of Rockport, Mass., finds the ratings inconsistent: ''The criterion shifts all the time. What was R a few years ago would be PG today. You see some horribly violent movies and they'll be PG.''
Despite its flaws, ''I think it's good to have some kind of rating system,'' says Mr. Huston, who has a 15-year-old daughter. ''Even if it's broad, vague, and not particularly accurate, it is a help. At least there is some kind of safeguarding.''
Some parents would like to see initials such as ''L'' for language or ''N'' for nudity added to the ratings.
''It would be good to find other designations to go with PG so I could be alerted to what my children might be exposed to,'' says Martha Horn of Hingham, Mass. Mrs. Horn has a daughter, 15, and a son, 13. To keep up on current films, she reads reviews, talks to other parents, and watches movie review shows on television.
Jack Valenti believes parents sometimes expect too much from the ratings.
''All the rating system does is give cautionary warnings. Parents must do the rest,'' says Mr. Valenti, who founded the system in 1968. ''They must take the care to research and guide the moviegoing of their children. If they don't care, the rating system is barren of any meaning whatsoever.''
Movie ratings are only initial tools in judging whether or not a film is appropriate for youngsters.
''Profanity, violence, sex, and nudity are the aspects of movies that tend to get rated. Movies are not rated on quality. The letters (PG and R) were never designed to do that for anybody,'' says Peggy Charren, president of Action for Children's Television. Even as a warning system she believes the ratings have failed.
''The letters have become meaningless,'' she says, adding that the G rating has virtually disappeared.
''People associate G with movies for young children,'' Mrs. Charren says. ''It really eats into the box office.'' Even with otherwise ''clean'' movies producers will ''manage to put in a small piece of profanity to get rid of the 'horrible' G rating.''
Instead of letter ratings, Mrs. Charren would prefer to see short descriptions indicating the level of profanity, violence, sex, or nudity. ''There's a big difference between 'some' violence and 'very' violent,'' she says.
Some publications already incorporate this system into their reviews. Mrs. Charren advises parents to find a movie reviewer they can trust for reading about current and coming films.
''If parents want to have some effect on their children's viewing or their own, they have to know something of what the movie is about,'' she says.
Janey Beebe of Littleton, Mass., has found this to be an effective approach. ''The rating system is perhaps some guidance, but my husband and I read a review if the movie seems questionable or controversial,'' she says. ''I don't see any point to these graphically violent movies and I would like to see the reviews and ratings [be more explanatory].''
As children get older, ''at some point you give your best guidance and then let them make the choice themselves,'' says Mrs. Beebe, who has a daughter, 14, and a grown son. ''We talk it over and help them come to a decision about whether it is a worthwhile movie or not.''
Some parents say they are weary of the glut of fantasy films and the lack of substantive, well-crafted films that relate to real life. They also complain about superfluous violence and swearing.
Beyond clarifying the rating system, what can the movie industry do to improve its image?
''They could clean up their act,'' says Jim Huston, an actor who has had small parts in feature films. ''There are movies that are not funny, not entertaining, and not redeeming - not anything. There's a lot of that being pumped out. Hopefully it will burn itself out.''