School hrs. up to 8 periods is 5 hrs and 30 min including tifin time.
For no. of classes, please see the attachment, from where you may also calculate the school hrs. for several classes.
A sample allotment of times per class-
1st 4 periods: 4×40 = 160 min
Tifin = 30 min
Last 4 periods: 4×35 = 140 min
All total 330 min i.e. 5 hrs and 30 min.