“The bottom line,” writes Gene Munster in a note summarizing the results of Piper Jaffray’s latest survey of the aspirations of American teenagers, “is that 40% of students plan on buying an iPhone in the next 6 months while 19% of non-tablet owners plan on purchasing a tablet in the next 6 months.”

Wishes, of course, can’t always be iPads. As Munster’s chart below shows, teenagers invariably want more Apple (AAPL) devices than they get.

Last fall, 38% of the students surveyed said they planned to buy an iPhone within six months, but six months later the percentage who own one had only increased 11 points, from 23% to 34%.

Still, as Munster points out, “interest in buying an iPhone has correlated to future market share gains among teens.”

The same seems to be true of iPads. Of the 34% of teenagers in the latest survey who already owned a tablet, 70% had iPads, 19% owned Google (GOOG) Android tablets and 11% had Amazon (AMZN) Kindle Fires. Of the 19% who planned to buy a tablet, 80% wanted an iPad.

Piper Jaffray polled 5,600 students for this spring’s survey, half male, half female. Their average age was 16.3. Further demographic information — such as their family’s average income — was not provided.

Below: Results from the last five surveys.

Click to enlarge.