My dax is not working correctly

Hi sakuragihana 

You can create a kind of multiplier:

Multiplier = 

SUMX('Teacher Schedule', IF('Teacher Schedule'[StartTime]="0",0,1))

And then, modify your measure:

DayOfTeachCount = 
VAR SelectedWeekStart = MIN ('Teacher Schedule'[Date])
VAR SelectedWeekEnd = MAX ('Teacher Schedule'[Date])
VAR Starttime = VALUE(SELECTEDVALUE('Teacher Schedule'[StartTime]))
VAR Endtime = VALUE(SELECTEDVALUE('Teacher Schedule'[EndTime]))
VAR Result = 
        SUMX(
            VALUES ( 'Teacher Schedule'[Date]),
            SWITCH (
                WEEKDAY ( 'Teacher Schedule'[Date],2),
                1, IF ( 'Teacher Schedule'[Date] >= SelectedWeekStart && 'Teacher Schedule'[Date] <= SelectedWeekEnd, 1*[Multiplier], 0 ),
                2, IF ( 'Teacher Schedule'[Date] >= SelectedWeekStart && 'Teacher Schedule'[Date] <= SelectedWeekEnd, 1*[Multiplier], 0 ),
                3, IF ( 'Teacher Schedule'[Date] >= SelectedWeekStart && 'Teacher Schedule'[Date] <= SelectedWeekEnd, 1*[Multiplier], 0 ),
                4, IF ( 'Teacher Schedule'[Date] >= SelectedWeekStart && 'Teacher Schedule'[Date] <= SelectedWeekEnd, 1*[Multiplier], 0 ),
                5, IF ( 'Teacher Schedule'[Date] >= SelectedWeekStart && 'Teacher Schedule'[Date] <= SelectedWeekEnd, 1*[Multiplier], 0 ),
                6, IF ( 'Teacher Schedule'[Date] >= SelectedWeekStart && 'Teacher Schedule'[Date] <= SelectedWeekEnd, 1*[Multiplier], 0 ),
                7, IF ( 'Teacher Schedule'[Date] >= SelectedWeekStart && 'Teacher Schedule'[Date] <= SelectedWeekEnd, 1*[Multiplier], 0 ),
                BLANK ()
            )
        )
  Return Result