Hi Kathy! Welcome to the WBT world. KEEP IT UP! That's my FIRST bit of advice. Give yourself time to figure things out and the kids a little bit of time to adjust.
I use class/yes and it works great, but there are some things to consider and do to make it most effective. First, consider if you were in the middle of talking and you were IMMEDIATELY expected to stop when someone asked for your attention. I changed my expectations! When I say class/yes, I'd LIKE for everyone to stop and listen, but if they don't, I give them another chance.
If you need them to focus on something very important, use "hands and eyes" Also, make sure to reward them when do it right - give them a happy mark on the scoreboard. If many kids DONT respond, you can recognize a few individuals who DID do it - either by having the kids verbally recognize the student (Bobby responded right away, everyone, tell Bobby OH YEAH) or with tickets or positive stickers, whatever you may have (we are a PBIS school and hand out "positives" to our kids)
Also - Another teacher on this forum said he sometimes does sound with his class/yes. For example,
Teacher: Clap, clap, clap, "Class?"
Student: Clap, clap, clap "yes?"
Or
Teacher: Clap, Clap, bang on desk, "class class class"
Student, Clap, Clap, bang on desk, "yes, yes, yes"
I think this helps when it's noisy because kids hear the claps and banging and quickly join in.
Good luck and keep the questions coming!