After a summer of doing anything but school work, you gotta wonder, "How much do kids fall behind during summer vacation?"

It turns out, a lot.

This widely-cited report reviewed 39 studies on the subject and found the break from the classroom is "most detrimental for math computation and spelling."

How bad is it? Dr. Adiaha Spinks-Franklin is an expert in developmental pediatrics at Texas Children's Hospital in Houston.

"The research has found that students can lose up to three months of reading skills and up to two months of math skills over the summer break."

And that can have long-term effects.

The doctor says a student who doesn’t read 30 minutes a day can fall behind two to three months. The student who does read jumps ahead two to three months. That can mean a six-month spread.

Now you repeat that after every summer, and children end up being a year to two years behind their peers, just based on summer learning loss.

So, summer break can put some kids well behind their peers. You can start fixing that problem right now, our expert says, by pulling the family together, every day, for 30 minutes to read.

Research shows summer learning loss is also major contributor to an achievement gap between rich and poor kids "with low-income students facing the largest losses."