Hi @djwaldow and welcome!
It looks like you created a single row and added all of your columns and photos under it. This would work if all of your photos had the same aspect ratio, but it appears some of them do not, which is why certain photos are breaking the grid.
Instead, you want to create a separate new row for each set of 3 columns/photos since they are sized at 1/3. This will ensure they align properly.
As a side note, if you need further help with your theme, the author of Ed School does offer 6 months of free support with your purchase. You can find it here: https://themeforest.net/item/ed-school-elementary-middle-and-highschool-wordpress-theme/19618075/support
Hope that helps!