I think you need to fix your tables before moving onto forms. Actually, I see no reports nor queries--those too should be your focus before moving onto forms.
You have a real big issue with your relationships, mostly having to do with many to many relationships. These type of relationships are handled with a junction table (
https://support.office.com/en-us/ar...ionships-e65bcc53-8e1c-444a-b4fb-1c0b8c1f5653).
The simple example is tblParents and tblAdmissions. In your relationships a record in tblAdmissions can have multiple records in tblParents. But couldn't a record in tblPArents have multiple records in tblAdmissions? Parents have more than one kid. You address that situation with a junction table.
The more complex example in your data is between students and classes (and probably fees). You need to set up your tables to accomodate single students in multiple classes as well as single classes with multiple students.
That's your big issue, here are smaller ones that need to be addressed as ell.
[age] field is redundant when you have a dob field. Get rid of age field.
Tables with only 1 real field of data (autonumbers aren't real data) are unnecessary. There's no need for tblRelationships tblClass nor tbluMonths.
I've only addressed the tables in your Relationship tool. There are others which have issues as well, but because I am uncertain if you are actually using them I did not address them.
Again, fix your tables before moving onto reports/queries before moving onto forms.