I have a save that's teen dominant and they get school projects every Monday. Regular homework takes about 2 sim hours. Projects vary, if they do them alone or have help. Without help I'm going to guess about 3 sim hours though I can double check as I'm in my teen load currently.
Once they're an A student you no longer have to do homework every day to keep the A but it's still a good idea to do the projects on Monday or regular homework once in the week so the grade doesn't start to slip with the various prompts that may give them a slight loss in performance while at school.
Journaling takes about 1 sim hour.
The project could be bugged if it's taking that long to complete but you can sell them for 80 (finished) and 100 (never worked on) and buy them from kids activities for 100 and each has a skill so if you want a skill that's more in line with your sims goals etc.
Otherwise you can try to debug by shift clicking the project. I've never had one take a full week to complete but only a few hours. I'll update the exact amount of time when I can.
Once my students are A grade I sell projects for the 100 every other Monday (helps with bills) and do homework instead on the Mondays I sell projects.