SeeD exam - Lv up Seifer?

I was wondering something.

I'm starting playing FFVIII again and when I get to Dollet to do the SeeD exam, if I kill off Squall & Zell, and spend ages Leveling up Seifer and getting lots of GF AP...

Does Seifer's level remain with him for the rest of the game?

For instance if I get him upto level 20 before he leaves the party (when Selphie joins) but keep everyone else at Lv 8 or so, when I come to spank him at (SPOILER)Edea's Parade thingy will he still be at Lv 20 when my three minions heroes are still at only Lv 8?

No, he levels up with Squall.

:p and i kill seifer and get zell and squall to nab all the experience

I'm fairly sure (I haven't checked recently, but from my understanding of the system) that he doesn't keep his old level. Seifer will be at Squall's level, unless Squall moves past his cap.

No he doesn't. Just for the hell of it (and to see if killing a massive number of enemies in Dollet did anything for your initial SeeD rank) I leveled Seifer up to like 50. He was still at level 8ish when I fought him for the first time (I hadn't leveled up).