I absolutely agree with Sound Before Theory. As a general music teacher, I have learned to love the moment when I first introduce the musical staff. This is because prior to doing so, we have spent MUCH time playing solfege singing games. The kids get incredible involved, especially because it's competition. Here is how I develop "sound" first, then theory.
We play a game called "Sol-La-Mi" in which the students MAY NOT sing the phrase "Sol-La-Mi" (usually based in D Major). I echo sing simple solfege patterns (increase complexity for older kids), but if the students hear the words/melody "Sol-La-Mi", they must ALL raise their hands and cover their mouths. If one person sings even a little portion of the phrase, I get a point! If they all raise their hands when they hear Sol La Mi, the class gets a point. If I trick them by singing La Sol Mi instead of Sol La Mi, and everyone raises their hands, I get a point. However, if just ONE students sings La Sol Mi, they can save their whole class from giving me a point!
We play in 5 rounds. The class progresses to the next round after they beat me in their current round.
Teacher sings using solfege and Curwen hand signs. Keep Sol-La-Mi simple and on it's own. Don't leave the round until all the class raises their hand for Sol La Mi.
Teacher sings on a hum and with Curwen hand signs, the students must TRANSLATE my hum into solfege when they echo it back. They don't get penalized if they don't translate it correctly, but I always repeat it so they can translate it correctly. Keep Sol-La-Mi simple and on it's own.
Round 3: Sing using solfege and Curwen hand signs, but use Sol La Mi in the context of a larger musical phrase. EX: Sol-La-Mi Mi Sol.
Round 4: Same as round 3, but with humming and translating.
Round 5, Same as round 4, but only provide the FIRST Curwen hand sign.
After several weeks of playing this game and developing their sense of pitch, We'll begin to use our hands as a "hand staff" (pinky on the bottom, thumb on top). I'll choose which space or finger is "sol", and we'll play Sol La Mi while pointing to the pitches on our hand staff (replaces Curwen Hand Signs). I'll move Sol around to different lines or spaces each lesson just so they get the concept.
Eventually, I use Noteflight and write the short melodic patterns we've been singing onto the staff. I'll use the COLOR option to color "sol" a certain color, and then I'll ask the students, "If the blue starting note is "sol", can you figure out the rest of the melody? I am always amazed at how well they sight-sing on the FIRST try! Then I have the joy of saying, "See! Reading notation from the musical staff isn't hard!!!"
Sol-La-Mi is a weekly occurrence and huge part of our routine, but these kids are getting SO good at solfege and pitch relationships because of it!