Baltimore County police said yesterday thay have arrested 41 high school students and 12 adults as a result of a drug investigation in which undercover police posed as students.

As many as 90 more suspected student drug dealers at five county high schools may be arrested, according to Capt. Joie A. Talley, a police spokesman.

"We've arrested students ranging from straight-A scholars to students who have been known to police," said Talley, who said the arrests were made after undercover police purchased quantities of marijuana, hashish and barbiturates from the suspects.

County School Supt. Robert Y. Dubel said the investigation began last December after several principals requested permission to have police to resolve drug problems at their schools.

"There will be some criticism over allowing undercover police on school property, but we felt the problem was serious enough to warrant the action. We think it is necessary to do this to protect all of our students," Dubel said.

The arrests began Wednesday when police called parents of suspected students and told them to bring their children to local police stations, where they were subsequently charged.

Three male police cadets and one policewoman posed as students and used $1,000 in police funds to purchase mostly "Colombian" marijuana at a cost ranging from $3 to $25.

The suspected students attended Hereford, Towson, Parkville, Woodlawn and Sparrows Point high schools.

The students charged with drug dealing, according to the county school superintendent, now face hearings at their schools as a result of which some may be assigned to attend evening classes, Dubel said.

"We want students to know how strongly we feel about it (drug dealing) and that we are going to take a hard line against it," he said.

The adults charged with selling conspiracy to sell and possession of drugs could face a maximum penalty of five years in jail and a $1,000 fine if convicted police said.