Parents have to pay for the last two years of BY high school (the fifth and sixth years – what would be considered seminary and college in the US, but in EY it is an extension of high school).
Are Bais Yaakovs really completely free? I hadn’t realized that.
A lot of people do send to private schools. It very much depends on the neighborhood. In one neighborhood that I know of, nearly all the Yeshivish people sent to the private school (the Bais Yaakov in that neighborhood did not have a good reputation at that time).