However, it all depends on the circumstances of the case.

First of all, any Search and Seizure should be 'reasonable' according to the U.S. Constitution. The Fourth Amendment is where your Rights against 'unreasonable' Search and Seizure are found. There is case law regarding searches in the school environment and those rulings are more lenient for Officers to search than other situations. Here are some possibilities.

Before an Officer can search your car, he needs 'probable cause'. For this situation, Probable Cause for searching a car is 'Facts and/or circumstances that would lead a reasonable police officer to believe there is contraband (illegal stuff) in the car.'

Example:

The Police Officer receives information that a student has Marijuana in his car in the school parking lot.

a) The officer goes to that car, but sees nothing to support the
information he was given--the officer does NOT have Probable Cause and CANNOT search.

b) But if the Officer goes to that car and sees what appears to be
Marijuana or Marijuana cigarettes or drug paraphernalia in the car. He now has Probable Cause to search the car.

c) OR, the officer goes to that car and smells the odor of Marijuana
from the car. Again, the Officer now has Probable Cause to search the car.

In the school environment, the rules are a little more easy for the School Staff and Officers. School Staff only needs 'Reasonable Suspicion' to search a car. 'Reasonable Suspicion' can be considered as information that leads to a 'reasonable' belief that contraband is in the car. If the information is from School staff, or involves weapons/school safety, the Officer only needs 'reasonable suspicion' to search. That 'reasonable suspicion' can be from the School Staff. If only the Officer's information is involved with the search, the standard is still Probable Cause

Example:

School Staff receives information that there is Marijuana in a student's car in the lot. Because of the source, or the method of the information coming to the staff, the School staff thinks the information is believable, or reasonable. The School staff contacts the Officer with their beliefs.

a) The officer goes to the car in the lot and looks in, but does not see
anything to support the information. The Officer CAN search because the source of his information is School Staff and Staff believes their information.

b) If the Officer goes to the car and sees contraband in the car, he now
has Probable Cause, which is more than 'reasonable suspicion', and CAN search the car.

Example:

Either the officer or school staff receives believable information that a weapon might be in a student's car. The Officer CAN search the car with no more than this 'reasonable suspicion'.