The consent age required by Luxembourg Law is 18 but the system is limited to the age of 16. Could you add a search field so schools can choose what consent age they require.
Also, if you change this could you change the wording on the Consent Forms to reflect this.
In the UK the seemingly arbitrary use of 16 causes us issues too. There is no age defined in UK GDPR when a student should be able to make consents by themself (although most lawyers seem to agree that 13 is a reasonable age). However we have a number of consents which relate to students but which should never be allowed to be completed by students (consent to allow them to drink alcohol for example).
This hard-coded and unchangeable option of age 16 makes the consents module next to useless for us here in the UK :-(