You should be honest with the new school and explain the facts. At the same time, write to the court that fined you in your absence, saying you had documentation and asking whether the case can be re-opened now you are aware of the summons, because you were not guilty of the offences. This assumes that you just forgot to comply with the seven-day notice to produce the documents. As you did not receive the summons, the court may be willing to reconsider the case for you. Hopefully, if your documents were all in order, you might not end up with a criminal record.