I'm going to have to deviate from the rest of you.....
As originally written 30+ years ago, the character of Sarah Jane Smith was decidedly that of a feminist. Now, I don't know about the rest of you, but in my experiences with feminists, they ordinarily don't do the whole "waiting around for the guy to return" thing. It's simply contrary to their nature & political ethos.
In the original series, Sarah Jane was very strong-willed, independent, and free-spirited. Sure, "School Reunion" makes mention of the fact that the Doctor couldn't take Sarah to Gallifrey. However, it FAILS to bring up the point that Sarah was planning on leaving anyway.
"School Reunion", IMHO, paints a very biased view of Sarah and, in effect, totally rewrites her character. There's no way she ever intended to "wait around" for the Doctor to come back. Remember, she stowed away on the Tardis in the first place, and it looked as if her own freewill was going to be responsible for her leaving. And, to a certain extent, it half-way was.
I'm also going to digress on the "jealousy" motiff between Rose & Sarah. 30+ years ago, the show was a sci-fi/drama mix of about 60%/40%. These days, however, the show has morphed into a 30%/70% mix. Is this bad? Perhaps, perhaps not. But (again, IMHO) I've found that the more "dramatic" a piece of television is, the less enduring it becomes. Thus, it's great the first time you see it, but re-runs just don't do it justice. I see the new Battlestar Galactica series in this way, though its sci-fi/drama mix is 10%/90%.
In short, the "jealousy" plot device, while seemingly engaging at first, really isn't anything that would inspire me to own these stories on DVD. And when I say "these stories", I'm talking about the new series stories that have used jealousy as a primary plot device. Honestly, all this "Mickey can't stand the Doctor" business is better left to shows like 90210, Dawson's Creek, Buffy, & similar tripe. The show survived for 26 seasons without reliance on such trivial & dismissive plot devices. Why does it feel the need to utilize them today? Please remove the soap from my science fiction!
My ranking of series 2 thus far:
The Christmas Invasion = 5.5/10
New Earth = 4.5/10
Tooth & Claw (or was that "Tooth & Nail"?) = 5.5/10
School Reunion = 6/10