The SSPX is "big" on catechizing, I know that. It's a huge piece of the puzzle when it comes to maintaining the Faith, which is why the SSPX takes an enormous interest in it.
But catechism classes for the various age groups (preschool, first communion, confirmation, teen, adult) is dependent on having enough "resources" -- and children -- to hold catechism classes.
Resources include parents willing to teach, classroom space, etc.
The more "integral" or "Catholic in my daily life" Catholics at the chapel, the better. Some people don't send their children to catechism class -- either they're lazy, or they plan to "teach their children at home". BAD MOVE. Religious instruction should take place in an extra-familial setting, to help ensure against loss of faith when children become teenagers and they start separating themselves from their parents. The Catholic Faith is not merely something "we as a family" do, but it goes beyond the family. Even if I leave my family, I shouldn't think twice about continuing to be a Catholic. Catholicism musn't just be something mom and dad do (or, worse yet, just mom does).
Of course, it's critical for children to practice the Faith in their daily lives, or a few minutes of instruction on Sunday won't be reinforced. So this is where the parents come in. But no matter how brilliant you are as a parent, and how well educated, it is important to send your child to a "traditional Catholic" catechism class -- it shows kids that there are other children and families who are Catholic as well. They get to see other adults teaching the same thing that you teach them.
A single SSPX priest can't teach more than one class, of course -- if that. Priests usually hear confessions before Mass, which is when other activities (Rosary, catechism classes, etc.) are going on. At our chapel, the priest teaches the adult class (about 20 minutes) then goes into the confessional to hear confessions from 9:10 till about 9:55.
Generally, the larger the chapel population, the more elaborate or complete the catechism class program will be.
Of particular note is the fact that the SSPX finds it important to catechize ADULTS too -- something often lacking in the Novus Ordo.