Will working as a Teaching Assistant as an Undergrad help for Graduate Admissions? Graduate admissions in an EECS field, either Ph.D or Masters. I know research experience is the most important but is having prior teaching experience also desirable?

I want to TA (it seems fun), but I'm debating on whether it will be worth it or not if it won't help me with either job prospects or graduate school.
Here's my opinion, based on being a faculty in a math department. When you apply to a graduate school, it's really a two-in-one application, i.e. there are two questions to be decided: will you be accepted or not; and if yes, then with or without financial support.

Having or not prior TA experience probably won't have any effect on your admission to the program. But getting financial support is a whole different story. If you have existing connections with a research professor in the department where you're applying, then he/she may be able to support you out of their research grants. Otherwise, especially for departments with a lot of service teaching &mdash; such as math or computer science, for example &mdash; having teaching potential can be decisive when it comes to awarding graduate assistantships. Of course, prior TA experience would be a huge plus for that.