I am with Sunny on this one, Have you tried to just add a list box for one of the fields from the table.
Try reordering the data model viewer in case it is just behind another table.
If they fail, try an exit script;
after your interval match see if it is created correctly, after that maybe try a Qualify statement, make sure it isn't being concatenated or join to another table.
school_name & '|' & date(begin_eff_date) & '|' & date(end_eff_date) as school_name_interval
The interval match requires ordinal values for the bolded field names - the dates must be proper numeric date values, and the match field (school_name here), must be an ordinal value that already exists in the data model - not part of the interval match load. The load under the interval match should return 2 fields only - unless you are doing an SCD style interval match with multiple parameters (like IntervalMatch(SomeDate, SomeAttrib1, SomeAttrib2)). An intervalmatch is usually paired with join --
Left Join (DATA)
IntervalMatch(TransDate) // a field in DATA
LOAD LowerDate, UpperDate Resident IntervalData;
In your case, the intervalmatch will not match anything, so nothing will be loaded, and therefore nothing will be visible in the table viewer.
Perhaps you could explain exactly what you are trying to do, along with a sample qvw containing representative data and someone will then be able to guide you.