All teachers can sign up for an educator account with the Portsmouth Herald. Click here. Then you will have 30 licenses to give out to students. This will allow you to see the newspapers going back to the day you signed up.
The public library has a digitized collection of the Portsmouth Herald going back to 2016, and earlier articles are available on microfiche. They have a Seacoast Online account, and patrons may visit the reference desk and search the online paper physically in person. OR a reference librarian will do a search for articles and email patrons PDF copies of relevant articles, including those on microfiche. Anyone can email libinfo@portsmouth.gov for this service.
The Portsmouth Herald archives are linked under "Research Databases" if you scroll down to News. I also linked it on the passwords document.