VLADIMIR STESHENKO'S son and daughter both got A's in Latvian in high school - and neither of them can speak a word of the language.So the children of the top Latvian government official on the nationalities question, like thousands of other Slavic inhabitants of Latvia who want to become citizens, must take Latvian lessons so they can learn enough of the language to pass a test. The language requirement is the wild card of a resolution passed by the Latvian parliament on Oct. 15 laying out how one can become a naturalized citizen of Latvia. The ruling calls for a "conversational level" of Latvian. But what that means and how it will be tested remains to be determined by the nationalistic Latvian parliament. The issue could exacerbate growing tensions between Latvians and Russians. At the same time, the May 5, 1992, deadline for Latvia's "law on languages" is fast approaching. Three years after the law was passed, all heads of state enterprises must know Latvian or lose their jobs. But little has been done to prepare for the deadline. Initially, 30 million rubles were designated to enforce the law, which aims to promote the use of Latvian in all public life. So far, according to Mr. Steshenko, 15 million rubles have been spent on teaching Latvian in schools and universities and only 1 million for the education of adults. Steshenko's department has asked for 6 million rubles to set up a center of adult education in Latvian, but little time remains. The poor knowledge of Latvian is easy to explain. Under Soviet rule, students only received two hours a week of language training, and some school districts got none because of a shortage of teachers. In contrast, full training in Russian was obligatory. Since the law on languages has not been taken seriously until recently, some observers conclude that the May 5 deadline will be ignored or extended. The point of the law is not to punish people but to foster the use of the national language, says Aina Blinkena, a top Latvian philologist who helped write the law. Erik Vebers, deputy chairman of the radical Congress of Latvia, chuckles over the significance of the law. "It is a legislative souvenir," he says derisively.