The Palestinians are generally left with a substandard life, especially those in refugee camps in Jordan and Syria, and even those that aren’t in camps have a much lower standard of living than the Jews (Israelis). This causes the Palestinians to try to better their lives, and this is attempted, at least by Hamas, through violence. With that in mind, when a group, like Hamas, is up against odds that are not in their favor, they have a duty to their cause to do everything in their power to win. This means that they will use civilians as shields, and will also use UN schools to hold weapons.
As for Israel, they have a right, and a duty to protect their people from attacks. This is the most basic service that a government can give to its people. Without that, there is no state. Given this, and given how Hamas must fight and take protection among civilians, there is no way to stop civilian deaths. It also means that every building in Gaza is technically a valid military target. The IDF (Israel Defense Force) does all it can to mitigate civilian deaths, but given the above, there will always be civilian deaths.
Conflicts are never good v. bad. The reasoning behind any conflict shows that conflicts are usually shades of plaid.