Instructional Time Increases in 5 States in the US
To read more, visit the National Center on Time and Learning
Josh Lederman of the Huffington Post quotes US Secretary of Education Arne Duncan:
"Whether educators have more time to enrich instruction or students have more time to learn how to play an instrument and write computer code, adding meaningful in-school hours is a critical investment that better prepares children to be successful in the 21st century."
This news item brings me back to a couple of previous posts on this blog:

And why is Grade 1 reduced to only half a day? In many countries with K to 12, Grade 1 is a full day.
“Unlike in other countries, many of our Grade 1 students spend hours walking to and from school,” Luistro says. “They are tired when they reach school. I want them to enjoy school, not (to feel) that (it) is imposed on them."
... Another aspect of the K to 12 plan that has been promoted without scrutiny is the length of instructional hours. This is intimately related to multiple shifts in schools. This area, as experts have warned, is likewise characterized ...

With the k+12 system, it is reduced to four hours per week, five hours for Science. “Kung saan tayo kinulang doon pa tayo nabawasan,” (there was reduction to where we are lacking). Originally, five hours is spent for English and Math subjects in a week and six hours for Science. With the k+12 system, it is reduced to four hours per week, five hours for Science.  
Then I came across another article in the Huffington Post, "Speaking Up for and Demanding Full-Day Kindergarten", by Marian Wright Edelman, which says:
For too many kindergarteners, though, one thing is still a throwback to the old days: going to school for only half a day. In order to master the skills covered in the Common Core Standards, the amount of time a kindergartener gets to go to school each day can vary from as little as two and a half hours to a full day of six hours. As even a five-year-old can see, that’s not fair. It’s time to stop demanding performance from children we do not give the supports they need to succeed.
Edelman also points to the following web page:
Read more at Strategies for Children
This is really a question of resources and prioritization. Short instructional hours allow for multiple shifts in schools. Limited classrooms and school buildings can therefore be used more than once during the day. Full time teaching can be defined as teaching two sessions, with each session, for example, lasting three hours. The irony is that DepEd's K to 12 adds two years at the end of high school. This addition comes with costs and additional infrastructure. The question we need to address is where would it be best to spend the money and extra time. Research should inform us....