I'm a Safeguarding Lead, secondary school.
The information you have given here is not at threshold for MASH.
They are asking you for information to see if you give additional contextual info that does raise it yo MASH threshold. They will have also asked the child. They evidently do not have any additional info that elevates to MASH threshold.
The change is sudden you say? To reach threshold for anything meaningful from Early Help, the school need to show a graduated responce (ie, we tried this, it didn't help, do we tried this, that also didn't help, so we tried this instead, that also hasn't helped so Early Help, can you try instead?).
In two weeks, they are at thr point where they have noted the change and are how monitoring. They may be offering some low-level in-school extra support - maybe mentoring, time out, mental health support, opportunities to talk to trusted adults. These form the graduated responce.
What to do next? Make it known to school you consent to, and request, an Early Help referral.