Still have the 11plus here and 13 plus, my DD has just taken 11plus today and we live in a small village about 10 miles south of Sleaford. Have just looked at girls only comp in Grantham, going to look at comp in Donnington called Thomas Cowley about 1/2 the size of St Georges Acadmey and results aren't too bad either think we prefer it as a nice small friendly feel to it.
Grammar schools are Carres for boys and Kesteven and Sleaford High for girls.
Also in Bourne there is the Bourne academy (formerly Robert Manning) and also Bourne grammar school mixed sex but very hard to get in as catchment area very small.
Are you going to be living in Sleaford itself as there are some good primaries but also most of the village schools are fab as well.
Thomas Cowley is a lovely friendly school, the children going there tend to be the ones who don't want to go to the larger schools in Spalding , Sleaford or Bourne. Robert Manning has a good reputation with SEN children but struggles slightly with higher achievers-especially in comparison to Bourne Grammar which takes the top 20% in the area.