When working with different service providers, I found that this was the best way for me to get organized! All I would do is enter in all of each students information on the top and then cross out all periods where students could not be pulled out. These pages ensured that students would not be "double booked" and also let me see at a glance who had not yet been scheduled.
To organize it even more, I gave each therapy type a different color of ink. IE
OT - purple
PT - blue
Speech - Green
Counseling - red