UPDATED: 10:41 a.m.

Lincoln High School officials say they regret not asking more questions before some high school musicians took part in a tax day event at Covell Lake in Sioux Falls.

The school band's drum line and some choir members had been told they would perform at a re-enactment of the Boston Tea Party on Wednesday and that Sen. John Thune had arranged it.

What they found were hundreds of protesters, some sporting politically partisan signs and T-shirts.

The district has a policy against participation in partisan events.

The school's assistant principal, Mike Klinedinst, says the musicians had been assured it was a nonpartisan event. He says the school and students were misled.

Thune's office said it had no involvement in the protest and that a staff member on her own time outside the office helped arrange the performance by the Lincoln drum line.