Ah, you do realize that per the description of
Spell Resistance: "A creature’s spell resistance never interferes with its own spells, items, or abilities."
So you're basically specifically nerfing casters of this race. Not that this is necessarily a bad thing, mind, as casters are at the top of the pyramid already, but you've potentially got some problems:
1) SR of 10 + 1/2 level is barely even a speedbump to anything CR appropriate. At, say, 10th, that's SR 15, and your opponents (who are at least as high a level as you, individually) are casting at +10 to their check, at a minimum. Which means they need a 5, for an 80% chance of success. Most the time, opposing casters will have a higher caster level than you have levels, and they may invest in spell penetration, so you're very often going to be looking at opponents ignoring the spell resistance entirely.
2) If you're not forcing everyone to be of this race, the majority of spellcasters will simply pick a different race, so the house rule has little net effect, except to make casters of that race relatively rare.
3) Spell Resistance is actually usually a bad thing for players anyway, as lowering it voluntarily takes a standard action, which is not something you can do when you're unconscious from damage and need a healing spell.
There's probably more.