Getting into private school for children and teens in The Sims 2 is quite easy, given a little time and effort. First, start increasing the cooking skill for one family member, the higher the better — at least to level 6 or so. Second, the headmaster won’t even come unless the kids are getting good grades and your family has a good amount of money. Third, make sure at least 4 rooms have a high environment score. Invite the headmaster in the morning when you’re ready, and he’ll arrive around 5. Greet him when he arrives and give him the tour of the nice rooms. Have the good cook serve a big meal such as pork chops, salmon, or even lobster, if you’re confident of your skill. Remember to click on the headmaster and call him for dinner. If you got a good enough score on the tour and had a good meal, these two things alone will get your score high enough. I usually do these things as quickly as possible to avoid a bug where the headmaster gets stuck on the lot.
Tip: Wait until all children are of school age, so you’ll only have to invite the headmaster once. Any toddlers that become children after the others are already in private school will not automatically be enrolled.