trackpad disabled when mouse is connected

I work for a K-12 school district, we are fairly technology oreinted. we have UF75 smart boards in each classroom, and we give out macbook Mid 2010's to all school students and staff. by defualt apple OSX 10.8.5 has set it to where it will override my trackpad when i connect my interactive smartboard. ive googled this and cant find where they keep the perference to disable this. i have a 10.6.8 machine and that was fairly easy to find this perference. any suggestions?