Slow synching times between PowerSchool and Schoology most often occur when assignment names are too long, contain special characters, or have spaces between the words in the title. Here’s a video that explains a solution.
Changing the assignment name in Schoology to something shorter, removing special characters, and replacing spaces between words with underscores (_) can help. Try a variety of solutions to find the one that works.
Finally, sometimes the syncs are slow and/or they don't work due to the system being really busy at the time you sync. Recommend you trying later in the day (or even the next day) to see if it works as expected.