Summer holidays affects language development?

The American Association of Speech and Language Pathologists have released a very controversial statement which asserts that children from poorer backgrounds are detrimentally affected by the 6 weeks summer holiday (or vacation to use their term). They feel that without the quality interaction experienced at school or nursery, children's language skills suffer. As a result they have published a list of activities and suggestions for parents to follow

http://www.asha.org/public/speech/development/Parent-Stim-Activities.htm

Is the same true here? What do you think?