This year (5772) the seventh day of Pesach is on a Friday, so the diaspora has an 8th day of chag on Shabbat but Israel does not. The diaspora will thus read Sh'mini on April 21, Tazria-Metzora on Apr 28, and so on through Bamidbar right before Shavuot. Israel, on the other hand, will read Sh'mini on April 14, Tazria-Metzora on April 21, and so on, waiting until Behar-Bechukotai to split a double (to end up at Bamidbar before Shavuot, as we expect).
There are three double parshiyot between April 14 and Shavuot. I would have expected the first one to be split in order to get the readings back in sync as soon as possible. (This would have meant being out of sync for only two weeks.) Instead, the calendars are not re-aligned until the last of the doubles. Why is that?