City              2017-18                     Item
0       Boston              100                       Primary
1       Boston              200                       Secondary
2       Boston              300                       Tertiary
3       Boston              400                       Nat'l average
4       Chicago             500                       Primary
5       Chicago             600                       Secondary
6       Chicago             700                       Tertiary
7       Chicago             800                       Nat'l average

City         2014-15         Item             New_column
0       Boston         100           Primary          100/400
1       Boston         200           Secondary        200/400
2       Boston         300           Tertiary         300/400
3       Chicago        500           Primary          500/800
4       Chicago        600           Secondary        600/800
5       Chicago        700           Tertiary         700/800