To answer this question, we need to analyze the given options and determine which group is most likely to have made a collection of money for the author. Let's examine each option in detail:

a) The students in the new high school:

- This option suggests that the students in the new high school collected money for the author.
- The author might have some connection with the students, such as being a former teacher or having some kind of relationship with the school.
- It is common for students to show support and appreciation for authors by organizing fundraising events or collections.

b) The teachers in the old primary school:

- This option suggests that the teachers in the author's previous primary school collected money for them.
- While it is possible for teachers to support and contribute to an author's work, it is less likely for them to organize a collection of money.
- Teachers may have other ways of showing support, such as recommending the author's work to their students or organizing book discussions.

c) Neighbours:

- This option suggests that the author's neighbors collected money for them.
- Neighbors may support and appreciate the author's work, but it is less likely for them to organize a collection of money.
- Neighbors may show their support in other ways, such as attending book signings or spreading the word about the author's work.

d) Social workers:

- This option suggests that social workers collected money for the author.
- While social workers may be involved in various community activities, it is less likely for them to specifically collect money for an author.
- Social workers may be more focused on providing assistance and support to individuals and families in need.

Based on the analysis above, option 'A' - the students in the new high school - seems to be the most plausible answer. Students often show support for authors by organizing collections or fundraising events. Additionally, the mention of a "new high school" implies a fresh group of students who may be enthusiastic about supporting the author's work.