In WebSched, you can set the exact requirements, restrictions and limitations that you need to impose upon your school’s schedule: [Scheduler | Setup course master builder specs]
For each course, you can setup:
If two or more courses must be taught in the same period, then designate one course as the Leader and the others as Followers.
To ensure specific courses are not taught at the same time, assign each of the courses the same Resource Group name (e.g. GYM).
For impossible periods, set the number of sections to 0 and the period to the impossible period.
For fixed periods, set the number of sections to the desired number and the period to the desired period.