Hi Desiree!
Thank you for bringing your question to the Disney Parks Moms Panel. As my mouseketeer isn't quite full time school age just yet, late August has historically been a time we have visited!
There are a couple things to consider when visiting
The Happiest Place on Earth and attempting to determine crowd sizes. As Disneyland Resort has a lot of local visitors, the first thing I'd recommend checking out is
block out dates for Disneyland Annual Passports. The Southern California Select is blocked out through the entire month of August so this will work to your advantage, but the Deluxe Passport releases it's summer block on August 19th so you may see any influx of Guests that week that haven't been able to visit throughout the summer or experience
Star Wars: Galaxy's Edge yet.
The next thing to consider is holidays! As Labor Day weekend falls in late August, you may see folks that are visiting from a land far, far away take a long weekend to come see Mickey. I'd say a day or two prior and after, you'll see a slight uptick, but that weekend specifically will likely be a popular time. The final thing I'd consider is
what's new throughout Disneyland Resort. As mentioned above, many Annual Passport holders may have not seen
Star Wars: Galaxy's Edge just yet, so this is going to be a draw, but beyond that I think you should be okay for any big draw.
While they aren't Disney published calendars, there are a plethora of third party sites that release crowd control calendars to give you an idea when's a good time to plan a trip. If you do a quick internet search for "Disneyland crowd calendar" you should have several resources at your finger tips. While they certainly are not 100% I have found them to be remarkably accurate in helping plan. I hope this helps in planning your upcoming visit! Please come back if we can help in any other way.
-Lindsey