I've installed four new ceiling fixtures - the first two in the living room were no trouble but the second two, which I installed in the bedrooms do not turn off. I've changed the switches (there are two switches in each bedroom) thinking that might be the problem but the lights still doesn't turn off so I've taken out the light bulbs and am now wondering what to do. Any ideas? Thanks!

Well, since we have no idea how you wired them there is not much we can do.
We would need to know exactly how you wired them, wire for wire, before even guessing what you did wrong.

So you replace four light fixtures. You replace two in the living room. The living room had a single switch.

You replace two fixtures in the bedrooms. Was that one fixture in each of two bedrooms or two fixtures in one bedroom. The bedroom fixtures use a set (2) of 3-way switches.

When replacing the switches, did you wire them exactly as the old ones were wired? The significant part of wiring a 3-way switch is getting the correct wire on the common screw.

Describe the wiring in the ceiling box.