Shuttering the parks in their autumn glory seems silly and unnecessary, but it is also a much more significant matter because the Park Service plays a vital role in education. More than 7.5 million schoolchildren participate in structured learning programs in the national parks every year. October is a prime time for school field trips and thousands of kids will be denied the chance to hear the deafening sound of the textile looms in Lowell or walk the hallowed ground of places like Gettysburg. Nothing taught inside a classroom can come close. The Park Service website — now shut down — is the government’s most-visited website. Its 900 links and curriculum study guides are a key resource for teachers and kids across the country. This year is the 150th anniversary of the Battle of Gettysburg, but schoolchildren who are assigned to write an essay on the Civil War will find a “closed” sign on the key Web links to this heritage.