THE generation gap has shrunk. At least many of the tensions that a decade ago tore at the family fabric - Vietnam, drugs, a booming affluent society whose values were tested at home and abroad - have faded somewhat, or parents and youths are looking at things more the same way.
Three-fourths of today's teen-agers report ''no serious problems getting along with any family members,'' compared with half of their counterparts 10 years ago, according to a National Association of Secondary School Principals survey. Some 55 percent of today's youth plan to enter a four-year college or university compared with 34 percent in 1974. Two-thirds of teen-agers say they regularly go to church compared with fewer than one-third a decade ago. Nearly half say they read as a leisure-time activity compared with a negligible 1 percent in 1974.
A majority of youths even say they like their schools - which contrasts with the widespread adult dissatisfaction with education that makes the news.
The young in 1974 said overpopulation and the environment were their chief worries. Today it's nuclear disaster and the threat of world war. Now as then, youth attitudes appear to reflect the leading agendas of their time. There's much to be grateful for in this easing of artificial generation divisions. There's work and pleasure enough for all ages to join in together.