Into the wild blue yonder by way of the stage; Grounded, by Todd Domke. New York: Alfred A. Knopf. 186 pp. $9.95. (Ages 7- 11.)

For younger readers (the main character is 11 years old), ''Grounded'' provides wonderfully zany reading.

Parker wants to build a glider. He also doesn't have any money. So, in the best Mickey Rooney-Judy Garland tradition, he and his fellow classmates decide to write and produce a show to earn it. But what starts out as a rather simple production of a Frankenstein play grows and grows and grows. As the premiere date approaches, there are rumors that the President of the United States wants to come see it and that singer Neil Diamond is going to be a guest star.

(And all this is just leading up to the original project, building and flying a glider - which Parker eventually does, and for which he is promptly . . . ''Grounded''!)

It may not seem like a very plausible plot line, when you think about it. But , in view of some of the inventive fantasies my best friend and I used to come up with - one can see that it at least hovers close to the realm of possibility.

One of the novel's major strengths is author Todd Domke's cast of characters. It's not hard to think back to one's school days and substitute real-life classmates for Parker's - a happy-go-lucky best friend and idea man, a stuck-up girl who wants to be a superstar, the class big shot. . . . My own personal favorite description is of the principal, who, according to one student familiar with Templeton in ''Charlotte's Web,'' ''could play the rat in person.''

In all, the book is good, clean fun that young readers will very likely enjoy.