For those who wish to specialise in training teenagers it is probably not unreasonable however there is nothing in the Act that concerns the average FI who is happy not to do it more than the regulation allows i.e once every 8 days. Regulated Activity must be read in context with "Activity related to Children"
REGULATED ACTIVITY RELATING TO CHILDREN
Regulated activity: general
1 (1) An activity is a regulated activity relating to children if—
(a) it is mentioned in paragraph 2(1), and
(b) it is carried out frequently by the same person or the period
condition is satisfied.
2 (1) The activities referred to in paragraph 1(1) are—
(a) any form of teaching, training or instruction of children, unless the teaching, training or instruction is merely incidental to teaching,training or instruction of persons who are not children;
In most cases teaching children is incidental to the purpose of a flying club.