Returns a list of the graduation years for students in a given grade this year.

SchoolGrades.rb

#!/usr/bin/env ruby
%w[date].each{|lib| require lib}
class Integer
	def ordinal
		cardinal = self.abs
		digit = cardinal%10
		if (1..3).include?(digit) and not (11..13).include?(cardinal%100) 
			self.to_s << %w{st nd rd}[digit-1]
		else
			self.to_s << 'th'
		end
	end
end

# Number of grades to compute the graduation years for. 
# K-12 - 13
# K-8 - 9
grades = 13

this_year = Date.today.year

grades.times { |y|
  grade = grades - y - 1
  if (grade == 0)
    pretty_grade = "Kindergarten"
  else
    pretty_grade = "#{grade.ordinal} Grade"
  end
  puts "#{pretty_grade} - #{this_year + y + 1}"
}