Insertion anomaly in database design

I want to design a DB for school, where marks for students will be scored. But i got stuck at a point with my current design where i want to insert student marks. My current DB design at broader level is something like:

-------------------       -------------------      ------------------
STUDENTINFO       |       |  EXAMS          |      | taught_in      |  
-------------------       -------------------      ------------------
   reg_id         |       | examID          |      |  t_cisId       |
   cis_Id         |       | examname        |      |  subjectcode   |
$otherAttributes  |       |                 |      |  t_id(auto-inc)|
__________________|       |_________________|      |________________|


-------------------       -----------------       ------------------
|ClassInSchool    |       | Subjects      |       |Result          |
-------------------       -----------------       ------------------
| classes         |       | subjectcode   |       |   regId        |
| section         |       | subjectname   |       |   examID       |
| cis_id          |       |_______________|       |   t_id         |
|_________________|                               |__scoredmarks___|

Now Issue is : In result table i want only those records to be inserted in table for which following condition satisfies:

1. A student should be a registered student (Satisfied by regId).
2. Marks should be inserted for valid(existing) exam (satified by examId).
3. A student who studies particular subject in a class, then marks should be inserted for those subjects only. This is where i am facing issue.

E.g, In sec A of class 7, English is taught. then For a student studying in 7A only marks for English can be inserted.

In my design if in sec B of 7 class, Maths is taught, then i can insert marks for a student for Maths who is studying in 7 A.

I want to handle this behaviour at database level only, otherwise i have to handle this in Java side.

Note: regId, examID, t_id are F.K. I have used similar names here for F.K to make it understand pictorially.