Hikashop Filter Module Issue

Currently I have added a custom field 'School' for the products, which the product is belongs to which school. (One product might have more than 1 school). Besides, for the user login, every user has their belongs school too. (One user might have more than 1 school).

In the frontend, I have display the filter of the schools according to the user belongs to (For example, user 1 belongs to school 1 and school 2), the school filter option will only show school 1 and school 2.

Until here, there is no problem.

But there will be wrong displayed, when a product have more than 1 school. For example, product 1 have school 1 and school 2. I can only view the product 1 under one of the schools (school 1 and school 2). But supposingly should be under both of the schools (school 1 and school 2).