Legally he can be issued a warrant for his arrest if he is a no show. This is not a legal cost you can afford either. He needs to show and plead his case to the judge and attorneys.
If he is an apprentice for a union they usally have some sort of set up for jury duty and monitery reimbursement.
If he shows his jury summons to his boss, his boss should understand that legally he has to go.
Most companies have a compensation system in place unless they are really small. Ours you turn over your "jury paycheck" signed and they in turn pay you your normal days wages minus shift differentials. If he works for a small company that does not do this then he does need to plead his case with the judge and possibly get his boss to write a letter stating the only compensation he will receive is the jury pay while he is away from the job.
I would not ignore this unless you are planning a move out of the area soon. Not a situation you need if money is tight.