What do you mean by yearbook photos? All seniors get their own half page to do with what they wish, many kids team up to get a full page (2 kids), or 2 full pages (4+) - and so on. Many times a big group from a particular dorm will do a page. Students will have gotten multiple emails regarding these deadlines. Parents or other family members may put together a page or part of a page and pay for it. I think a full page is somewhere around $400 - again, I believe my email was clogged for months with this info long after I paid during the early bird discount time. Just look at his old yearbooks and you will see what I mean - some senior pages are fancy, some are not. Most families do something personal from childhood - and some have professional staged photos (not the norm, however). Some do just a quarter page, and some do a full if they have a lot of pics.
It does take a while for them to return emails/phone calls (it is a club - albeit a really large organized one) and these kids are busy. I do remember that you just uploaded photos to a central website (and pay) and they (the PEAN staff) will format it for you. They will send a proof for you to approve later on. You may also format your own page - the guidelines were also on the website that we linked to for page payment.