Sentence:  It would authorize the Texas Education Agency to establish county-wide day schools for the deaf in counties of 300000 or more <WSD>population</WSD> , require deaf children between 6 and 13 years of age to attend the day schools , permitting older ones to attend the residential Texas School for the Deaf here . 
Meaning of the word marked with <WSD> tags:  (statistics) the entire aggregation of items from which samples can be drawn