Personally I always find it bad taste to not credit the photographer.
Now, insofar if this use falls under the academic exception would really depend on whether or not the website is generating income. The academic exception was really created so teachers and professors could present copyrighted materials to students in a class setting without the fear of being sued. It was not created however for academics to be allowed to use that material to promote themselves and earn additional income.
So, if this is truly a blog that is providing information to his students for a specific class that he is teaching without generating income directly, then it would be an okay use. However, if he is generating income directly from his blog, or plans to in the future, it is a violation.
Google came under assault for something similar a fews year back. In the beginning of the 2000s, Google scanned every book in a few University Libraries (I forget which ones) and decided to post it online, violating the copyright of all the authors, photographers, graphic designers, illustrator, etc. Google tried to use the academic use exception to defend itself, but since Google would be generating income (from ad sales) from this site, it was not a successful defense.
In any event, you could notify the photographer and he could issue a request to have the site page taken down. It usually takes about a day for the request to go through. If he is a foreign photographer, suing for damages is probably not possible.