A Clear Lake High School teacher was arrested on school grounds Tuesday after officers said he showed signs of being high on marijuana and was spotted hiding hash oil in an office bookcase, according to police.

School administrators called Lakeport police after Michael Alan Oleson, 58, of Kelseyville was seen driving erratically on two streets leading to campus, according to the department.

Oleson is a special education instructor, according to the Lakeport Unified School District website.

About 2:45 p.m., officers evaluated Oleson in an interview in an administrative office on campus and determined he was showing signs of being under the influence of marijuana, police said.

While police were speaking to administrators outside the office, an officer saw Oleson hiding in a bookcase what police later found to be a small amount of marijuana hash oil, according to the department.

Oleson was arrested on suspicion of driving under the influence of marijuana, possession of marijuana on school grounds and concealing evidence. He was booked into Lake County Jail where he underwent additional drug screening.

You can reach Staff Writer Christi Warren at 521-5205 or christi.warren@pressdemocrat.com. On Twitter @SeaWarren.