That would most likely depend on
Essentially, they can. School is public property, and if a teacher has good reason to search your bag, there are no laws preventing them from doing so.
In some schools, there is the requirement that at least two staff members be present.
Yes. A search may be conducted on reasonable suspicion and probable cause, but the simple fact that illegal drugs were proven to be in the backpack is more than enough reason that it needs to be checked to see if there are any more. Police are not required to take your word for it that you have given them the entire collection of contraband.
allowing student to have a backpack search
Secure your backpack better - report them to authorities (school administration or the police) be sure to have proof against who you are accusing, however.
just search
Yes, you are not necessarily required to be present.
The police got a search warrent in order to search the suspect's house. The suspect would not allow the police to search his home without a search warrant.
Yes all police officers need a search warrany in the UK
Yes, the officer may search. Police may search a building if they reasonably believe a valid search warrant has been issued. They do not have to possess the search warrant.
Police can search a private home if they have a warrant to search a house. There may be some exceptions under the Patriot Act.
Under the Constitution, which is the law of the land in the USA, Search and Seizure is legal when the police have received a search warrant normally signed by a local judge. There are some situations, depending on the jurisdiction (where the search takes place) in which the police don't require a search warrant signed by a judge.
Yes they can search it
There is no consent needed from anybody when there is a valid search warrant in play. The court gives the police the right to search by granting the search warrant.