changing a bell scedule in the late in the year

[LoraO]

We have discovered a possible mistake in our bell schedule.  This may be the reaseon our attendance is not going to the state properly.  We have an AM and a PM attendance set up for our 1-5th grade   The problem is a time of 8am to 9am was attached to both start and end times.  I tried to just edit the PM start/end time and I got the message" It is not possible to edit the bell scedule period at this time as it will impact the total attendance minutes for 3,000 students"   How do I fix this

[JeffG9]

Create a new Bell Schedule. 

[LoraO]

This would need to be changed back to the start of the year.  I would need to create the new bell scedule period, create the new attendance class.  Drop the students old attendance class,  (first delete the attendance), t Change their schedule to the new class and hen recreate their attendance.  Does this sound correct.  That's a lot of work for 425 students , or is there an easier way.