Please see below some useful information from the recently launched DfE campaign 'Moments Matter, Attendance Counts':

From the first day of term to the last, the small moments in a school day make a real difference to your child. 

Everything you need to know about school attendance - https://educationhub.blog.gov.uk/2022/09/02/back-to-school-week-everything-you-need-to-know-about-school-attendance/

If you are unsure whether you should send your child into school the NHS website - 'Is my child too ill for school' is a useful tool - https://www.nhs.uk/live-well/is-my-child-too-ill-for-school/

It is never too late to benefit from good attendance:

More than half of pupils who were persistently absent (<90% attendance) from school in Year 10 and then rarely absent in Year 11 passed at least 5 GCSEs, compared to 36% who were persistently absent from school in Year 10 and 11 (2). Attendance is important for more than just attainment - regular school attendance can facililate positive peer relationships which is a protective factor for mental health and wellbeing (3).

(2) Missing Children, Missing Grades | Children's Commissioner for England (childrenscommissioner.gov.uk)
(3) Mental Health and Attendance at School (Chapter 1) - Mental Health and Attendance at School (cambridge.org)