Data Merge for Yearbook and arranging photos in rows

I am designing a yearbook, and I am trying to use data merge to import student photos. I need to import the photos so that they are arranged in five columns and six rows, and arranged alphabetically by row. Every time I go to data merge and use the multiple record layout, it is placing one student's photo at the start of every row and leaving the rest of the row blank. I have selected the option "arrange by rows first" but it still doesn't work.

Now, I have my data source organized so that there are just three columns: the first is my @IMAGE, the second is the first name, and the third is the last name. I did notice that if I went in and reorganized the data so that there were 15 columns, with these three placeholders repeated five times, and then used that data source, the data merge would then import correctly, but that seems really cumbersome and counterintuitive for data organization. Also, I have over 600 pieces of data that I would then have to go and reorganize if that is the only way to get data merge to import in rows.
Is there something I'm missing or another way to do this? If I have to rearrange my data, is there any way I can take the three columns of data in an excel sheet and redistribute it across 15 rows?

Also, I'm not interested in a $129.99 addon if that is what you're recommending. 

Thanks!