Gina,
Welcome to the community!
Let me say that I'm not a desktop user and will let others with more expertise answer specific Desk top questions. I will say, however, that material hold down is often 50% of the battle. In my case... I seldom do the same project twice and tend to use Double stick tape by the case. I generally cut with an onion skin strategy, this allows ALL the tape to contribute to holding under the heavy cutting loads, making it easy for the tape on just a particular part able to handle the last .015". (Ask if you want more information)

One brand name of the multicolor plastic is "Color Core" any Sign supply house will stock it.

Tell me more how you are using the Bot on the Middle School level!

Steve