Students may enroll for only one assistant position per semester. All assistant positions are for one semester and are open to grades 10-12. 9th Grade students are not eligible to be assistants. Learning recommendation: Staff permission. Listed below are some of the areas in which teacher assistant credit can be earned. Students are allowed to TA one time during high school. If you were a TA previously at Liberty prior to 2013-2014 school year, you can TA one more time.