Several state have made a commitment to extended school days and/or school years so as to provide more “time on task” for education. The greatest benefit seems to be the allotment of increased time for science, music, art, word language, and social studies instruction without reducing the needed time in ELA and Math.
This article from the University of Scranton, points to a 2% return on a 10% investment in extended time. That is, for the 10% increase in school costs, some schools got a 2% increase in scores. Not cost effective, except when one considers that Massachusetts, a consistent high-scorer in NAEP, has extended education time.
Some formats for extended time include a British-type trimester calendar with rotating sessions, teachers, and classes. (Think 2 sessions on; one session off)
Here’s an article. Let’s think before we over-react or over-calculate our increased pay: