NATIONAL COMPUTER <NLCS> SEES EARNINGS GROWTH National Computer Systems Inc expects fiscal year earnings to improve by about 20 pct, the company told analysts, although it said the April 30 first quarter should show "down earnings and virtually flat revenues." Chairman Charles Oswald said National Computer has taken steps to improve margins. He said revenues are expected to increase modestly because of the company's decision to downsize its leasing business, nonrecurring revenueslast year from a one-time Texas teacher assessment project and the impact of the discontinuance of products last year. Oswald said National Computer's first quarter results will be down as a result of a major financial systems sales last year, a higher effective tax rate and the increased number of shares outstanding. The company said the next three consecutive quarters should demonstrate "excellent earnings growth."