Tonight marks the start of the eight day festival, Passover, in the Jewish calendar. Passover (or Pesach in Hebrew) celebrates the freedom of the Israelites from centuries of slavery when they left Egypt en masse on the last night of the Ten Plagues.
In the Jewish faith a holiday begins at sunset of the previous day, so while Saturday April 7th is the first day of the festival this year, observing Jews will celebrate Passover starting tonight. The first two days will be filled with food, family and friends, and are considered full-fledged holidays (no work!), as are the final 2 days. The 4 middle days are semi-festive and some work is permitted.
I've noticed that for some Jewish and Christian festivals, the Jewish festival days don't line up so nicely with the break periods given by ESDNL (i.e.: Hanukkah might start a day or two after or before the kids get out for Christmas break), so it is nice that Easter break lines up so nicely... much more festive when there is no school, I think! ;-)
Here are some interesting links and sources for Passover: