The discovery in drinking water of lead, copper and bacterial contamination due to aging plumbing at La Mirada Elementary School in the San Ysidro School District should be a wake-up call for all local — and state — districts with older schools. San Ysidro officials are so worried about the possibility of water contamination at two other campuses with older buildings, Smythe Elementary School and San Ysidro Middle School, that they are distributing bottled water at all three schools until it’s clear that water from their fixtures is safe to drink.