they were under the old retirement plan, now they would have to work to the age of 62.5.
Actually there are now three levels relating to receiving "full retirement": Rule of 80 (became a member of the Teacher Retirement System before 1991), Rule of 90 (after 1991) and Rule of 90 Modified (after some point in the 2000s). The numbers relate to when you could retire with a combination of age and years of service. The Modified rule is the one with the specified age requirement. Most Rule of 80 people will be gone in the next decade but regular Rule of 90 will apply for quite a while.
No matter what "Rule" you're under, the basic defined benefit is 2% of salary times years of service. There are special rules relating to how many years of salary are averaged to get the figure for multiplying by 2%. For a classroom teacher on the standard schedule with a graduate degree, let's use $45,000 as the average. With 30 years of service, the multiplier becomes .60 (.02 * 30) so the defined benefit is $27,000/year ($45K * .60).