13-Year-Old in Possession of Marijuana

My question involves criminal law for the state of: CA
My 13 year old was found to have marijuana with him at school. I have two questions:

1) School sent employee to police station to have tested: they did not call police to collect from school. Is this legal? How do we know that what was given to police was what was found in my son's bag?

2) School contacted police to make report after they found it to test positive. Police did not contact us or my child for a week and then really did not care if we had our child make a statement or not. We declined to have him speak to the officer after officer told us it did not matter either way. Officer states my son will more than likely be referred to a program he must complete as he has no prior record. This is all fine with me but she then stated that it will be on his record as an arrest for possession and stay until we have it expunged at 18. Is this correct?

We were not allowed to see what was taken from our son's back pack but we were told it was a very small amount. Should we hire an attorney to fight this as he is so young and it will be on his record as an arrest for posssession or should we just except the charges?

What does your son say?

1. Possibly... which employee? Was this employee in a position to collect evidence?

2. I don't understand your point here. Are you asking if the police have to tell you in a given amount of time that they are going to be arresting your son?

No, they don't.

We also don't know what your son said to the school official that originated the confiscation.

As the poster above asked, what did your son say?