Everyone’s pace is different, so I would say a “good pace” is the one your school and teachers are maintaining. Granted, if you want to work ahead or if your school schedules assignments unfavorably, then go at a pace suitable for yourself. As long as you’re meeting the deadlines set by your teachers, that should be a good pace.
Not falling behind comes down to making good choices with your time and productivity and setting a schedule you know you can follow. Some might suggest working ahead and if that works for you, go for it! But the key to not falling behind and meeting deadlines is to focus on your work and avoid procrastination as much as possible.