Does display order have numbers like 1,2,3? try this
Sort(Filter(Available_Schools, Enabled_Class = "Y"),DisplayOrder,Ascending)
Also you don't need seprate column for this if there are only few values. Let's say your values are January, February ,March. Alphabetically they will be sorted as February, January ,March. So what you can do is
SortByColumn(ListName,ColumnName,["January","February","March"])
So, it's not necessary to give sorting order as Ascending or Descending.