A yearlong dream of strutting down Pennsylvania Avenue in bright purple uniforms in front of national televison cameras and President Ronald Reagan as part of the Jan. 20 inaugural parade came to a bitter end yesterday for 200 band members in Lewiston, Idaho, a small, isolated northcentral town.

Because of what inaugural officials are labeling "an unfortunate misunderstanding." Lewiston High School band members and their director believed for months that they had been chosen to march in the parade.

Yesterday, they learned that not only were they not being invited, the fighting Bengals from Lewiston had never even been considered.

While Lewiston students were near tears yesterday, students at Cardozo High School here in Washington area expected to be squealing with delight today when the inaugural committee formally announces the names of 10 military, 12 high school and 8 college bands chosen to participate in the parade.

According to Bill Hart, a parade coordinator, Cardozo is the only Washington-area high school band selected by the committee. This is the second national honor for the Cardozo band, formed 10 years ago with secondhand instruments, ragtag uniforms and a band director's dream. The Northwest District school aslo has been chosen to march in the 92nd Tournament of Roses Parade in Pasadena, Calif., on New Year's Day.

More than 400 high school and college bands sought invitations to Reagan's parade, Hart said. Besides Cardozo, the Virginia Military Institute Regimental Band in Richmond has been chosen to march in the 110-step-per-minute parade, Hart said. VMI's band was selected, in part, because Reagan starred in a 1937 film called "Brother Rat," which dealt with hazing problems faced by first-year students, or rats," at VMI.

Lewiston's Bengals apparently were unaware of changes Reagan's committee made for selecting bands this year. In order to keep the parade less than one hour, the committee decided to invite fewer bands than for previous parades, when one band from each state was chosen to march. In 1973 and 1977, Lewiston's band won the right to represent Idaho. This year, Gov. Jon Evans, a Democrat, once again chose Lewiston's band.

Believeing their sport was secure, band members launched a series of fund-raisers -- car washes, bake sales and finally a hugh community-wide spaghetti dinner. The students raised $16,000, the school board kicked in another $12,000 and students promised to pay $550 apiece out of their own pockets. Many of the students took on part-time jobs, school officials said, to pay for the weeklong trip to Washington with a stopover in New York City.

In November, a Lewiston delegation came to Washington to inspect the hotels where the band would be staying, check out the restaurants and walk the parade route.

Everything was going according to schedule until Band Director Ed Williams got a telephone call last week from the band director at the University of Idaho. The university band never had asked to take part in the parade, but had been invited. Had Lewiston gotten its invitation?

Confused, Williams called inaugural officials who told him they didn't have Lewiston on their list because it never filed a formal application. Stunned, Williams said the committee neve told him such an application was needed, although committee officials claim all high schools that participated in previous parades were notified.

It's really upsetting this community," said Diane Pettit, a reporter at the Lewiston Tribune. "These kids worked so hard. A lot of their brothers and sisters had gone to the parades before. It's a real blow."

"It would be unfair to let them come now," Hart said."We had to turn down dozens of bands. We can't accept Lewistons now."

"It really seems unfair," said Pettit. "The university band didn't even want to go, but it got invited. These kids want to go."

Even if the University of Idaho, which was invited because of its band's reputation, declined the invitation, Hart said Lewiston will not be invited. "We will go to our alternate list and they aren't on it," he said.

"What's ironic," said one Lewiston official, "is that Reagan carried Idaho with 68 percent of the vote, the second highest plurality in the nation. i

"He sure won't carry Lewiston next time around."