Conservative lobby group Family First says a proposed law change banning schools from randomly testing or searching students for drugs will make schools unsafe.
The Government has proposed the change in the Education Amendment Bill.
Police lawyers advised last year that random or blanket searches are illegal. The proposed legislation stipulates police can help schools with searches only when there is evidence of students carrying weapons or drugs.
Family First national director Bob McCoskrie says hundreds of students are being caught with drugs each year.
He says parents and schools are trying to give children a zero-tolerance message on drug use and the Government should be reinforcing, not undermining, their efforts.