I've had those stretchy M&S ones in the past for dd & taken a tuck in either side of the waistband. I didn't think they wore that well though, she got 'pulls' in the fabric very quickly (having said that she was at primary and hard on trousers so maybe secondary is a bit different).
Takver I wouldn't consider them for DD2 as she's a complete tearaway and still at primary, but for secondary wear they rock. By that age girls don't tend to do many running type games at break (DD1 does netball and basketball training but wears PE kit for this). Hers are immaculate after 3 months (though the length is now spot on because she has grown, she will need the 14-15 size soon. Sigh) The high cotton content is worth it for me.
M & S now do slim fit trousers online. DD1 is (13) is 5'2" and a size 4/6 the age 12 ones fit her beautifully. I haven't seen them instore to try, but you can return M&S easily if they don't work for you. They were a revelation for her - she's NEVER had school trousers fit before. Of course, she's now about to start a school where they have to wear a skirt.
Try Next they do trousers in regular and slim fit.
I bought the slim fit from m&s for ds2 who starts secondary in September too, but they were still miles too big for him. The next ones in age 11 (and he is average height, just skinny) fitted just right and are true to the size chart. You can have them delivered to your nearest Next store free. (And no I don't work for Next)