Schools shall provide continuing education for those students who are determined to need additional time to achieve the outcomes defined in KRS 158.6451, and schools shall not be limited to the minimum school term in providing this education. Continuing education time may include extended days, extended weeks, or extended years.Those statutory words create our extended school services program, a key element of the original KERA design.
In the beginning, the "extended year" summer school option was seen as a key part of the program, especially promising for students who needed to make up one or two high school credits to stay on track for graduation.
Sadly, in the beginning, ESS also had a $53 million budget for 1991-92, which would have made a strong summer school fully possible. Instead, to handle a 1992 shortfall, Kentucky cut $25 million from that one program. ESS never regained the lost funding. Funding peaked at $36.5 million in 1999-2000, and is back down to $13 million for 2008-09.
When we look at the giant number of extra students in ninth grade (discussed here and here), we should remember summer school as the first great KERA retreat. If the original appropriation had kept up with inflation all these years, we'd be spending $80 million this year, and my hunch is that the bulge would be far smaller.
Source: the 1992 OEA annual report discusses the ESS cut, and can be downloaded here.