Grass Valley police arrested two high school students Wednesday on suspicion of stealing an $800 police helmet.The headgear was taken Tuesday from a traffic officer's motorcycle while he was attending an educational trial at Nevada Union High School."Some miscreant took our motorcycle officer's helmet," Grass Valley Capt. Dave Remillard said Wednesday before the helmet was found. "I would classify this as highly disappointing. ... (Traffic Officer Brian Hooper) works very hard, and he puts in a lot of extra hours doing presentations. He was there doing his job."The officer was at the school for the trial of a woman charged …