IN THE FALL OF 1980, Washington's public school system underwent a dramatic and important change. Officials decided that children in the early grades would be measured in reading and arithmetic every half-year--and those who did not meet the standards would repeat the semester. There were some naysayers--including one principal who grumbled that some students would be in the third grade until they grew beards. There are no signs of stubble yet, but now administrators are having second thoughts about the policy. They should stick with their first thought.

The whole idea of this policy was not to make fools of little children but to find those having learning troubles and to help them master basic skills before moving on. Supporters of this policy-- and we were in that number--noted at the time that initial results would be disturbing, as they had been in other systems with similar policies: at first, failure rates are often high. But in time, children and their parents can begin to understand that progress may require more, or special, effort.

The numbers did prove staggering: at the midyear point in the 1980-81 school season, half the 21,622 students in the first through third grades were not advanced--note that we do not say "failed"--because they had not mastered either math or reading skills. In the second year, more were promoted because the system decided to permit "transitional" promotions for those who had mastered one of the two skills. This year, the rate was even better, as 84 percent were passed.

But now, School Superintendent Floretta McKenzie and some board members seek to end the midyear policy. Mrs. McKenzie argues that it takes up too much of the teachers' time, that it has disillusioned students who were retained and that it suffers from a lack of resources for the system to run it well.

Take those arguments one by one: if this kind of monitoring of the most fundamental skills of anybody's education takes too much of the teachers' time, either those teachers need help or they are in the wrong business. If the policy is disillusioning little children, how does that graduate who can't read, write or add feel after he's promoted right on through? And if a school system can't afford to educate its charges, it's in deep trouble.

It need not be. At this point, the proposal to revert to annual promotions has been sent back to a school board committee for further study. Barring a much better case for it, that is where it should stay.