I approve of the PDF score (always nice to see scores in progress).
Regarding the Alto Sax part... they are all in the lowest register of the alto. A few times you hit low Bb with the 2nd Alto part, which is literally the lowest note on the Alto unless you put your foot in the bell. (Then you can get an A, but it's a useless talent).
I would recommend bumping both parts up an octave (or 2), as it will provide a much nicer sounding Alto section. (Instead of Altos trying to be Trombones). The same is roughly true with the Tenor. Bump it up an octave if it's hitting middle C on the score. Saxophones can ALWAYS go higher, but when you go low, there isn't much room to go.
The other thing that I would bring to your attention is the fact that most of the parts are incredibly similar. The simplicity of the piece is definitely a bonus for it being a High School Marching band piece, but don't oversimplify. When the Flutes, Saxes, and Clarinets are playing the exact same lines, you are really limiting yourself and actually hindering the music. I would recommend looking at those lines (Flutes, Alto & Tenor Sax, Clarinet) and figuring out where you can single out a specific instrument. For example, in the higher parts of the song, have the flutes play (and maybe add your trills like you wanted), while the Saxes are hitting half notes. This will add a much greater dynamic to the piece, and gives the musicians some ownership of their specific parts.
You did a great job on the low brass section of the score, and the piece could really benefit from that attention to detail with the woodwinds.
Looks like it's off to a really good start though. Good luck!