There are a couple of approaches you could use. First, use Help->Send Feedback to send some feedback to the Omni developers that you want the ability to have repeats with some knowledge of the calendar (only M-F, only the 1st Monday of the month, etc.) While you are at it, you might also ask for the ability to have a repeating action that stops after some number of repeats, or on some date.
While you wait for that to be delivered, you could continue with your daily repeat, but Saturday morning, use the
Defer script posted on the forums to bump Saturday's repeat to Monday.
Another approach is to set up more than one repeating item, repeating on a weekly basis instead of daily. Instead of having one "do math problem set" action repeating every day (and needing to be deferred over the weekend), you would have 5 "do math problem set" actions, each with a start date a day after the previous one, repeating weekly. No futzing around on the weekends required, but a little more effort to set up.