"Tell Me Why," an innovative video encyclopedia for children, is a handy learning tool that will not collect dust on the shelf as the family set of information books often does. These videos can make children love the excitement of learning and acquire extensive information about nature and historical landmarks.

One is tempted to remark: "Tell me why it wasn't done long ago."

Nevertheless, it has arrived, and the series may be one of the video industry's best resources for supplementing a child's education. The first six volumes came out in August. Six more are due in April, an additional six next August. The final eight will complete the 26-volume set early in 1989. They are being released by Prism Entertainment at $14.95 each.

The innovative series is based on Arkady Leokum's set of books that sold more than a million copies, inspired by questions most often asked by Leokum's own children. More than 50 questions are posed and colorfully answered on each 30-minute tape: Why wasn't America named after Columbus? Why aren't all trees green? Why does the moon shine? Can butterflies smell? Why is the ocean salty? How do flowers grow? Why is the White House white? Where do you find a grasshopper's ears?

The first six volumes deal with questions young people ask about: 1. Space, Earth and Atmosphere; 2. Water and Weather; 3. Flowers, Plants and Trees; 4. Gems, Metals and Minerals; 5. Insects; 6. Americana. The second six tapes, due in April, will be titled: 7. Life Forms, Animals and Animal Oddities; 8. Birds and Rodents; 9. Mammals I; 10. Mammals II and Spiders/Scorpions; 11. Fish, Shellfish and Other Underwater Life; 12. Prehistoric Animals, Reptiles and Amphibians.

A look at this series will offer a youngster the opportunity to get a leg up on fellow students. Even a single video will send 'em off to school the next day with a little extra bounce in their steps.

View-Master Video has just put out a new release for the younger ones to add to its "Kidsongs" series, "A Day at the Circus." This is No. 9. Sales covering the first eight titles are approaching 500,000. The videos run about 25 to 30 minutes and usually include about 10 songs as well as an illustrated sing-along song book. They sell for $19.95, but the latest release has a $5 rebate in the package as part of a Christmas special. (The success of this series has prompted a syndicated TV show, "Kidsongs," now in more than 100 markets.)

The first eight titles in this series are: "A Day at Old MacDonald's Farm," "Cars, Boats, Trains and Planes," "I'd Like to Teach the World to Sing," "Good Night, Sleep Tight," "Sing Out America," "A Day With the Animals," "What I Want to Be" and "Wonderful World of Sports."