Delightfully easy to introduce fraud when you have all of the ballots in one place.
Having 16 year old students as election judges is a big concern. Seasoned election judges are needed in a General Election, especially a Presidential election. They know how to deal with provisional ballots, question the authenticity of a person, count the ballots correctly after the polls close, handle emergencies...
One thing about senior citizen election judges, they are familiar with those who vote in their precinct and spot a fraudster.