D'Addario are my favorite strings for all levels.
Honestly, if a student can afford the Helicore it's better, but most my beginners buy Prelude.
I discovered the Kaplan (profeasional/soloist level) about 12 years ago and that's all I use for my personal instruments ever since.
D'Addario strings are Made in USA and of great quality with a very affordable price for what it is.
Also, the moment I started using the Kaplan on my cello, all my intonation issues were gone like magic!