Keeping kids out of R-rated movies has long been a task that movie theaters have performed grudgingly. After all, many action pictures aimed at the teen market are rated R, which technically excludes anyone under 17 from being admitted without a parent. But now, some theaters are trying out a new system, under which kids whose parents have been willing to grant them blanket permission to see R-rated films can bypass the system simply by flashing “the R-card”. The Motion Picture Association of America, which assigns the ratings, is not pleased.