YOU HAVE HEARD the complaints about high school graduates who can't write a clear, grammatical sentence. Perhaps you have uttered some of them. One highly promising response, the Virginia Writing Project, is coming to the end of its federal grant. That makes it an interesting test of President Reagan's hope that states will pick up the most worthwhile of the programs that the federal government had previously supported. A bill to give it a small but necessary state appropriation has now been introduced in the House of Delegates. Even in a time of great stringency, it deserves to be passed.

In the three years since it began its work, the Writing Project has drawn some 7,000 teachers into its programs--one out of every 10 teachers in Virginia. The basic idea is to induce students to write more, and more frequently. Writing, after all, is like playing basketball, or playing the piano. If you only do it once in a while, you can't expect to do it very well. The Writing Project, based at George Mason University, is a leader in the long march back from that unfortunate period in American education when all the tests were multiple choice and written papers were required only in those English courses known to be hard and therefore to be avoided. That's being changed, but not without a lot of work and a little money.

The Writing Project costs about $600,000 a year, most of it for the summer workshops for teachers who will then go back to their own schools and colleges and repeat the instruction there. Local school systems pay a third of it--not a bad indicator of local support--and colleges and universities throughout the state put up another third. It's the last third for which the legislature is now being asked. It's an investment in the most important kind of capital, and it promises a time, perhaps a decade from now, when you may suddenly realize that you haven't been hearing those complaints about young people who can't write English.