Untitled

var numOptions = 50; //the highest numbered checkbox field id after the "_"; #1 is reserved for "open".  You **Should** be able to skip numbers and be ok

function addEvent(element, eventName, handler) {

	if (element.addEventListener) {
		element.addEventListener(eventName, handler, false);
	} else {
		element.attachEvent("on" + eventName, handler);
	}
}

function loadEvents() {
	for (var i=2; i<=numOptions; i++) {
		var thisCheckBox = document.getElementById('schoolStatuses_'+i);
		if (thisCheckBox)
			addEvent(thisCheckBox,'click', unCheckOpen);
	}
	var openBox = document.getElementById('schoolStatuses_1');
	addEvent(openBox, 'click', unCheckOthers);
}

function unCheckOpen(e) {
	var allUnchecked = 1;
	for (var i=2; i<=numOptions; i++) {
		var thisCheckBox = document.getElementById('schoolStatuses_'+i);
		if (thisCheckBox)
			if (thisCheckBox.checked) allUnchecked = 0;
	}

	var openBox = document.getElementById('schoolStatuses_1');
	if (allUnchecked) {
		checkBox(openBox);
	} else {
		unCheckBox(openBox);
	}
}

function checkBox(checkBoxItem) {
	checkBoxItem.checked = true;
}

function unCheckBox(checkBoxItem) {
	checkBoxItem.checked = false;
}

function unCheckOthers(e) {
	for (var i=2; i<=numOptions; i++) {
		var thisCheckBox = document.getElementById('schoolStatuses_'+i);
		if (thisCheckBox)
			unCheckBox(thisCheckBox);
	}
}

<body onload="loadEvents()">